Jacob switches from the sin of pride to the grosser sin of immorality. Alma later in the Book of Mormon labels immorality as “most abominable above all sins save it be the shedding of innocent blood or denying the Holy Ghost” (Alma 39:5), Jacob here calls it the grosser sin. Grosser means a more serious sin in nature or behavior; unrefined, crudely vulgar. Both pride and immorality are called an abomination before God. In the days prior to Lehi leaving Jerusalem, Jeremiah spoke to the men who had known the way of the Lord, and the judgments of God, but had altogether broken the yoke, he said:
7 How shall I pardon thee for this? thy children have forsaken me, and sworn by them that are no gods: when I had fed them to the full, they then committed adultery, and assembled themselves by troops in the harlots’ houses.
8 They were as fed horses in the morning: every one neighed after his neighbour’s wife.
9 Shall I not visit for these things? saith the LORD: and shall not my soul be avenged on such a nation as this? [Jeremiah 5:7–9]
The men in Jacob’s day seem to fit the chastisement of Jeremiah, and the sins of pride and immorality can be seen in Jeremiah’s prophecy. Our day also fits that description. Jacob said, “they understand not the scriptures,” and justified their immorality because of what was written about David and Solomon (Jacob 2:23). Today, for example, we hear the claim that Jesus did not condemn the woman taken in adultery, which supposedly justifies that sin. These people do not understand the scriptures. Jesus told the woman to “go, and sin no more,” which acknowledges that adultery was a sin, but did not condemn her because the law of Moses required witnesses and the Pharisees, pricked by their own guilty consciences, would not witness against her (John 8:11).
Jacob records that the many wives of David and Solomon were an abomination to the Lord (Jacob 2:24). Some, in their pride, would say this contradicts what the Lord revealed to Joseph Smith.
37 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, they have entered into their exaltation, according to the promises, and sit upon thrones, and are not angels but are gods.
38 David also received many wives and concubines, and also Solomon and Moses my servants, as also many others of my servants, from the beginning of creation until this time; and in nothing did they sin save in those things which they received not of me.
39 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; and, therefore he hath fallen from his exaltation, and received his portion; and he shall not inherit them out of the world, for I gave them unto another, saith the Lord. [D&C 132:37–39]
President Joseph Fielding Smith has responded to these critics:
There is no contradiction between Jacob and the Doctrine and Covenants. Jacob declared that the Lord prevented the Nephites from practicing plural marriage, and called attention to the fact that David and Solomon sinned taking wives that the Lord did not give them, which is true. However, the key to the situation may be found by reading further the account in Jacob. The Lord said: “For if I will, saith the Lord of Hosts, raise up seed unto me, I will command my people; otherwise they shall hearken unto these things.” [Jacob 2:30]
It is not strange that the Lord did not condemn Abraham and Jacob (Israel) upon whom he founded the house of Israel; nor did he condemn the parents of Samuel, the great prophet, not others who had plural families. He did not condemn Solomon and David for having wives which the Lord gave them.
Turn to 2 Samuel 12:7–8, and you will find that the Lord gave David wives. In reading the Old Testament you will also find that Solomon was blessed and the Lord appeared to him and gave him visions and great blessings when he had plural wives, but later in life, he took wives that the Lord did not give him. For evidence of this, turn to 1 Kings 11, and read it. You can tell these people that the whole house of Israel was built on the twelve sons of Jacob who had four wives— Mothers of the house of Israel.
Jacob is making a general statement. The Doctrine and Covenants gives specific examples, and is supported by accounts as cited by President Smith.
The Lord knows that immorality destroys a nation. Therefore, the Lord led the people of Lehi out of the immoral nation of Judah by his power, to raise up unto him “a righteous branch from the fruit of the loins of Joseph” (Jacob 2:25). If Jacob’s people had become immoral, they would not have accomplished the purpose of their being brought to the promised land. Because they were beginning to become immoral, the Lord commanded Jacob to declare his word to them (v. 26).