Having addressed the sinners, Jacob gives preventive measures to the pure in heart for maintaining their purity. Alma follows this pattern when warning his son, Corianton, of the seriousness of immorality (see Alma 39). The first thing Jacob suggests is prayer. Alma instructs us to “watch and pray continually that ye may not be tempted above that ye can bear, and thus be led by the Holy Spirit” (Alma 13:28). Paul admonished the Corinthians: “There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it” (1 Corinthians 10:13). Combining these admonitions, the Spirit will provide the way of escape. Moral transgressions are usually made in the dark and in secret. We must avoid enticing situations by following the directions of the Spirit. However, if we fail to heed his promptings, the Spirit withdraws, and we are left on our own. We must do our part. Prayer is also appropriate for parents. They should pray that their children’s purity will be maintained. Likewise, friends may pray for the purity of their friends. Jacob promises that God will not only comfort those who pray in faith, but will protect them by sending down justice upon those who seek their destruction (Jacob 3:1). How God intervenes is not stated, but it is often unnoticed or unseen. God watches over his children, and knows how to intervene without revoking their agency. We must listen to the still small voice.
The second preventive measure, given by Jacob, is “to receive the pleasing word of God, and feast upon his love” (v. 2). The word of God plainly tells us what he has commanded concerning chastity and morality. While the world presents many opposing, and often appealing points of view, those who study the scriptures and listen to faithful church leaders and loving parents, will know the Lord’s commandments. The Lord’s love will be poured out upon those who keep themselves clean. Both preventive measures speak of “firmness of mind,” suggesting a commitment to maintain purity, and not waver in any degree in one’s thoughts or actions.
The Lord warns of destruction by the Lamanites if those who are immoral do not repent. Immorality will destroy a nation, and although the Lamanites had been cursed they were not immoral (v. 3). Another principle is added by Jacob that had been taught earlier; the Lord will lead the righteous out from among them before a nation is destroyed (v. 4; see also 1 Nephi 17:37–38). That prophecy is fulfilled later (see Omni 1:12–13).