Jacob told them it was true that David and Solomon did indeed have many wives and concubines, and what they had done was abominable in the sight of God. On first reading, this passage creates some confusion because it almost sounds as though the Lord always considered multiple families to be an abomination. The Lord clarified it in a modern scripture in which he said that the "many wives and concubines" of David and Solomon were an abomination in his sight to the extent that were taken without the sanction of the Lord. Here is the way the Lord says it: "David also received many wives and concubines, and also Solomon and Moses my servants, as also many other of my servants, from the beginning of the creation until this time; and in nothing did they sin save in those things which they received not of me."
2 The Lord goes on to say that David's great offense was in coveting the wife of Uriah. Solomon's offense was his action at the very end of his life when he tried to hold the kingdom together by entering into numerous political marriages. The scripture says that "when Solomon was old," he took unto himself 700 princesses of various aristocratic families, and 300 concubines as well.3 Many of these were heathen women and idolaters.4 However, there is no record of Solomon having any children through any of these marital alliances. They appear to have been undertaken when he was too old to have children, but were considered necessary in order to maintain political solidarity -- a common custom in those days. However, they were unauthorized and clearly an abomination before the Lord. The only mitigating circumstance seems to be the fact that this breach of an otherwise brilliant life occurred after Solomon appears to have entered into a period of senility just before his death.
5 Jacob said the Lord wanted the people to realize that their arrival in America was no accident. They were brought here by the power of God's mighty arm. It had been done so that the Lord could raise up a righteous branch of those who were descendants of Joseph. The Lord was determined not to allow the Nephite men to enmesh themselves in the abominations of ancient times. Jacob then laid down the general and basic law of marriage under which all men and women are obligated to live unless they receive a direct revelation from the Lord to do otherwise. The law is that a man must not have save it be one wife and concubines he shall have none.