A: I think that to understand what Mormon meant when he told Moroni that "Charity...endureth forever" as it applies to us, we need to back up a few verses and look at the attributes of charity:
Moroni 7:45 And charity suffereth long, and is kind, and envieth not, and is not puffed up, seeketh not her own, is not easily provoked, thinketh no evil, and rejoiceth not in iniquity but rejoiceth in the truth, beareth all things, believeth all things, hopeth all things, endureth all things.
When Mormon describes these attributes, he is not just describing the characteristics of an abstract principle, nor is he solely describing the attributes of Christ and His life. Mormon details the components of the pure love of Christ to the end that we can learn what it takes to shape our lives and our selves to resemble the life and person of Jesus Christ.
Moroni 7:47 But charity is the pure love of Christ, and it endureth forever; and whoso is found possessed of it at the last day, it shall be well with him.
The whole point of the gospel is to help us to become like Christ so that we can gain eternal life. The crowning principle of the gospel, and the most enduring attribute and quality of Christ's life is charity, and unless charity becomes our most defining attribute and quality as well we cannot truly become like Christ.
Peter tells us that if we wish to become "partakers of the divine nature" we must progress in becoming like Christ until we reach the pinnacle of Christ-like development in which we too are possessed of the same love wherewith Christ loves.
2 Peter 2:2-7 Grace and peace be multiplied unto you through the knowledge of God, and of Jesus our Lord, According as his divine power hath given unto us all things that pertain unto life and godliness, through the knowledge of him that hath called us to glory and virtue: Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust. And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge; And to knowledge temperance; and to temperance patience; and to patience godliness; And to godliness brotherly kindness; and to brotherly kindness CHARITY.
Note that charity is presented as the crowning virtue among virtues that define the divine nature of which we are meant to be made partakers. Charity is the greatest virtue to which we can aspire, and without it all other virtues, deeds, "righteousness", faith, and even the performance of great miracles, essentially amount to nothing, and therefore cannot profit us.
1 Corinthians 13:1-3 Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal. And though I have the gift of prophecy, and understand all mysteries, and all knowledge; and though I have all faith, so that I could remove mountains, and have not charity, I am nothing. And though I bestow all my goods to feed the poor, and though I give my body to be burned, and have not charity, it profiteth me nothing.
Mormon elaborates on this principle and informs us
Moroni 7:46 Wherefore, my beloved brethren, if ye have not charity, ye are nothing, for charity never faileth. Wherefore, cleave unto charity, which is the greatest of all, for all things must fail—
(I wish to note here that Mormon uses a phrase in common with Paul when he says "charity never faileth". When Paul uses this phrase he uses a form of the Greek word "pipto" which means to fail, fall, or stumble. I only mention this because Peter uses a similar Greek word for the word "fall" in a verse at the end of this article.)
Here Mormon explains that the supremacy of the virtue of charity stems entirely from the fact that all other efforts, such as the aforementioned faith, miracles, deeds and righteousness, must fail-and yet charity endures. This permanence is unique to the principle of charity-the enduring quality of the pure love of Christ. Christ endured what he endured, in spite of all of his faith, righteousness, miracles, and deeds, for no other reason than that he loves us. Christ chooses to extend his merits and mercy and grace to us, in extending His righteousness to cover our sins, solely out of His love for us and for no other reason.
John 3:16-17 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
John 15:12-13 This is my commandment, That ye love one another, as I have loved you. Greater love hath no man than this, that a man lay down his life for his friends.
Romans 5:8 But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us.
Romans 3:23-25 For all have sinned, and come short of the glory of God; Being justified freely by his grace through the redemption that is in Christ Jesus: Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
If we want to have charity, if we seek to become like Christ, our love has to endure the same way His love endured. Our love has to endure the crosses of the world, and despise the shame of it, and we have to be willing to lay down our lives for our God and our neighbors.
1 John 3:16 Hereby perceive we the love of God, because he laid down his life for us: and we ought to lay down our lives for the brethren.
"Without this love for God the Father and our fellowmen we are only the form of His Church—without the substance. What good is our teaching without love? What good is missionary, temple, or welfare work without love?" (Dieter F. Uchtdorf, "You Are My Hands," Ensign, May 2010, 70).
If we truly wish to be counted among Christ's disciples, then we ought to follow Christ's example, in which he endured all things out of love, and in order to secure the happiness and well-being of His brethren.
Hebrews 12:2 Looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is set down at the right hand of the throne of God.
What joy was set before Christ, that he would endure the shame of the cross? Was it the promise of a place at the right hand of God? Not entirely. The joy that moved Christ to endure the agony of the garden and the torment and shame of the cross was the prospect of bringing us with Him to stand together at the right hand of the throne of God. Christ's joy, his work and his glory, comes from bringing to pass our immortality and our eternal life.
Ether 12:33 And again, I remember that thou hast said that thou hast loved the world, even unto the laying down of thy life for the world, that thou mightest take it again to prepare a place for the children of men.
If we seek to become like him and obtain that eternal life which he has we must also be willing to endure what he endured.
2 Nephi 9:18 But, behold, the righteous, the saints of the Holy One of Israel, they who have believed in the Holy One of Israel, they who have endured the crosses of the world, and despised the shame of it, they shall inherit the kingdom of God, which was prepared for them from the foundation of the world, and their joy shall be full forever.
This presents us with a dilemma-how can we endure what he endured? We are mortal, frail, weak and imperfect-how can we endure what the perfect Son of God endured? How can we lay down our lives for our friends and for our God and in any way make that sacrifice equal the one that Christ made for us? The real answer is that we can't. But we can make our sacrifices for God and others RESEMBLE Christ's sacrifice. Notice that what Jacob said in 2 Nephi 9:18 is that we have to endure the crosses of THE WORLD, and despise the shame of it. What are the crosses of the world? Are they things like suffering, cruelty, envy, selfishness, wrath, inner evil, iniquity and lies? How can we endure such an onslaught? How can we endure and overcome these crosses of the world? Let's return to Moroni 7:45:
And charity suffereth long, and is kind, and envieth not, and is not puffed up, seeketh not her own, is not easily provoked, thinketh no evil, and rejoiceth not in iniquity but rejoiceth in the truth, beareth all things, believeth all things, hopeth all things, endureth all things.
Charity is the means by which we are enabled to endure, as Christ did, the crosses of the world and thereby are brought to sit "down at the right hand of the throne of God" to "inherit the kingdom of God". When we are filled with charity, we hope in all things, and hope enables us to "despise the shame" of the crosses of the world because "hope maketh not ashamed."
Romans 5:5 And hope maketh not ashamed; because the love of God is shed abroad in our hearts by the Holy Ghost which is given unto us.
Hope maketh not ashamed because if we are filled with God's love we have the power to Bear all things, believe all things, hope in all things, and endure all things. Nothing the world can do to hurt or destroy us can frighten or deter us because we are filled with the love of God. In this way charity, the perfect love of Christ, casts out all fear and shame.
1 John 4:18 There is no fear in love; but perfect love casteth out fear: because fear hath torment. He that feareth is not made perfect in love.
2 Corinthians 4:6, 8-10 For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ. We are troubled on every side, yet not distressed; we are perplexed, but not in despair; Persecuted, but not forsaken; cast down, but not destroyed; Always bearing about in the body the dying of the Lord Jesus, that the life also of Jesus might be made manifest in our body.
When the light of God's love, His charity, "hath shined in our hearts", we are enabled to overcome all things that we must suffer as we bear "the dying of the Lord Jesus"-i.e. when we endure as He endured. When we do this, and are filled with Charity, "the life also of Jesus...[is] made manifest" in our lives.
The quality of endurance which Mormon taught us is the hallmark of Charity is what enables us to become more like Christ. When we endure tribulation and suffering for His sake, and act for the good of others purely out of love and for no other reason, we will be purified by this process. This purification process is a necessary alteration in our fundamental character that we must each experience if we seek to become something that even remotely resembles Jesus Christ when He comes and we see him as He is.
Moroni 7:48 Wherefore, my beloved brethren, pray unto the Father with all the energy of heart, that ye may be filled with this love, which he hath bestowed upon all who are true followers of his Son, Jesus Christ; that ye may become the sons of God; that when he shall appear we shall be like him, for we shall see him as he is; that we may have this hope; that we may be purified even as he is pure. Amen.
Obviously we aren't anywhere close to where we need to be if we want to "be purified even as he is pure." But don't let that discourage you. Remember that you are mortal and normal--perfect charity that endures forever is an attribute of Christ because he is perfect and he endures forever. For the rest of us that is the goal to strive for, even if we don't feel like we're very close to reaching it any time soon. I think we are blessed for doing the best we can to love God and our fellow man, and as we pray "unto the Father with all the energy of heart, that ye may be filled with this love" (Moroni 7:48) The blessing that we are promised if we do this is that God will grant us the ability, as a spiritual gift, to develop more, and more enduring, charity. We have to pray for it because one: we don't have it, and two: We can only get it from God. How do we get God to agree to fill us with the pure love of Christ? We have to demonstrate our willingness and preparation for this blessing by gradually shaping our lives to resemble all of the attributes and qualities of Christ.
Colossians 3:12-15 Put on therefore, as the elect of God, holy and beloved, bowels of mercies, kindness, humbleness of mind, meekness, longsuffering; Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye. And above all these things put on charity, which is the bond of perfectness. And let the peace of God rule in your hearts, to the which also ye are called in one body; and be ye thankful.
This is the soul of Gospel living, and the one way to obtain "the peace of God" to rule in our hearts. All commandments, laws, and the teachings of the prophets are fulfilled when we keep the simple commandments to love God with all our heart mind and soul, and to love our neighbor as our self. As we do our best to follow the simple principles of the Gospel, line upon line, precept upon precept, we will naturally progress in our ability to love God and others. If we will learn to love God and our neighbors, God has promised that He will come and dwell in us and fill us with His perfect love, and we will be made "partakers of the divine nature" and of eternal life.
2 Peter 1:5-8 And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge; And to knowledge temperance; and to temperance patience; and to patience godliness; And to godliness brotherly kindness; and to brotherly kindness charity.
1 John 4:16-17 And we have known and believed the love that God hath to us. God is love; and he that dwelleth in love dwelleth in God, and God in him. Herein is our love made perfect, that we may have boldness in the day of judgment: because as he is, so are we in this world.
2 Peter 1:10-11 For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ. Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall: For so an entrance shall be ministered unto you abundantly into the everlasting kingdom of our Lord and Saviour Jesus Christ.