Jacob 3:6 - 3:10
Jacob 3:6 And now, this commandment they observe to keep; wherefore, because of this observance, in keeping this commandment, the Lord God will not destroy them, but will be merciful unto them; and one day they shall become a blessed people.
Because they do keep this commandment, they will be blessed and they will not be destroyed as I'm sure the Nephites wish the Lord would do. In the future they will be blessed as Lehi promised in his blessing to his grandchildren. They will be a thoroughly righteous people enjoying the blessing promised to the Nephites. (It looks as if keeping this one commandment can make up for a lot of other bad behavior which might be committed because of tradition and custom.)
Jacob 3:7 Behold, their husbands love their wives, and their wives love their husbands; and their husbands and their wives love their children; and their unbelief and their hatred towards you is because of the iniquity of their fathers; wherefore, how much better are you than they, in the sight of your great Creator?
Jacob tells the brethren that the Lamanite men love and honor their wives and their wives love their husbands. The Lamanite families are close and the children are raised in a manner that is pleasing to the Lord. The only difference between the Lamanites and the Nephites is the traditions the Lamanites were raised under and that is the fault of their fathers Laman and Lemuel. In spite of their traditions and life style, they are living according to gospel principles better than the Nephites.
Jacob 3:8 O my brethren, I fear that unless ye shall repent of your sins that their skins will be whiter than yours, when ye shall be brought with them before the throne of God.
Jacob is concerned that if they do not repent for these gross sins, their skins will darker that the Lamanites at the judgment bar of God.
Jacob 3:9 Wherefore, a commandment I give unto you, which is the word of God, that ye revile no more against them because of the darkness of their skins; neither shall ye revile against them because of their filthiness; but ye shall remember your own filthiness, and remember that their filthiness came because of their fathers.
Jacob now commands them in the name of the Lord, not to revile against the Lamanites. They are not to look down on them because of their skin color or their life styles. The Nephites need to look to their own sins and how they are treating their own families. The Nephites will be held accountable for their attitude towards the Lamanites, whereas the Lamanites will not because they don’t know any better because of their own traditions which again were put in place by Laman and Lemuel.
Jacob 3:10 Wherefore, ye shall remember your children, how that ye have grieved their hearts because of the example that ye have set before them; and also, remember that ye may, because of your filthiness, bring your children unto destruction, and their sins be heaped upon your heads at the last day.
Jacob wants the brethren to think how their actions are effecting their children. Because of their terrible example and if they do not repent, their children will end up like the Lamanites. They will be just as filthy and loathsome as the Lamanites which again Jacob reminds them came because of the wickedness of their fathers.