D&C 132

This revelation came about because the Prophet Joseph asked concerning plural marriage wherein teh Lord answered -

"...that inasmuch as you have inquired of my hand to know and understand wherein I, the Lord, justified my servants Abraham, Isaac, and Jacob, as also Moses, David and Solomon, my servants, as touching the principle and doctrine of their having many wives and concubines—
2 Behold, and lo, I am the Lord thy God, and will answer thee as touching this matter."  (Doctrine and Covenants | Section 132:1 - 2)

As we contemplate the doctrine of plural marraige, we must first understand that the Lord said -

"...hear me, and hearken to the word of the Lord: For there shall not any man among you have save it be one wife; and concubines he shall have none;
28 For I, the Lord God, delight in the chastity of women. And whoredoms are an abomination before me; thus saith the Lord of Hosts.
29 Wherefore, this people shall keep my commandments, saith the Lord of Hosts, or cursed be the land for their sakes.
30 For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people..."  (Book of Mormon | Jacob 2:27 - 30)

It is apparent that plural marraige is only approved and appropriate only when the Lord commands it.  When the Lord commands it, it overrides all other commandments for -

"Abraham was commanded to offer his son Isaac; nevertheless, it was written: Thou shalt not kill. Abraham, however, did not refuse, and it was accounted unto him for righteousness."  (Doctrine and Covenants | Section 132:36)

In the same manner -

"God commanded Abraham, and Sarah gave Hagar to Abraham to wife. And why did she do it? Because this was the law; and from Hagar sprang many people. This, therefore, was fulfilling, among other things, the promises.
35 Was Abraham, therefore, under condemnation? Verily I say unto you, Nay; for I, the Lord, commanded it." (Doctrine and Covenants | Section 132:34 - 35)

And thus -

"Abraham received concubines, and they bore him children; and it was accounted unto him for righteousness, because they were given unto him, and he abode in my law; as Isaac also and Jacob did none other things than that which they were commanded; and because they did none other things than that which they were commanded..."  (Doctrine and Covenants | Section 132:37)

But in David's case -

"David's wives and concubines were given unto him of me, by the hand of Nathan, my servant, and others of the prophets who had the keys of this power; and in none of these things did he sin against me save in the case of Uriah and his wife..."  (Doctrine and Covenants | Section 132:39)

This is because this action was contrary to the will and commandments of the Lord.  You will note that this commandment or authorization came by Nathan, a prophet of God.   Even though we may not understand the meaning of all things, in regards to plural marriage, it comes down to being obedient to the commandments of the Lord and His holy prophets, according to His mind and will.