Jacob 3

As Jacob concludes his remarks -

"...warning them against fornication and lasciviousness, and every kind of sin, telling them the awful consequences of them." (Book of Mormon | Jacob 3:12)

He also teaches an important doctrine to -

"...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." (Book of Mormon | Jacob 3:10)

It becomes clear that the Lord will judge all people in fairness. Each will be given a fair opportunity with their agency to come to Christ. But where a parent fails to teach their children properly, the demands of justice may fall upon the parents for the sins of their posterity.

In summary, Jacob counsels -

"Look unto God with firmness of mind, and pray unto him with exceeding faith, and he will console you in your afflictions, and he will plead your cause, and send down justice upon those who seek your destruction.
2 O all ye that are pure in heart, lift up your heads and receive the pleasing word of God, and feast upon his love; for ye may, if your minds are firm, forever." (Book of Mormon | Jacob 3:1 - 2)