Deut 6:6-7, Ps 78:5-8, 2 Tim 2:2
In the Old Testament, after Joshua died, the next generation did not know God, nor did they know what God had done. (Judges 2:10)
Judges 2:10 And also all that generation were gathered unto their fathers: and there arose another generation after them, which knew not the Lord, nor yet the works which he had done for Israel.
In the Old Testament, God commanded the people of Israel to teach their children about God and what God has done. (Deut 6:6-7, Psalm 78:5-8)
Deut 6:6 And these words, which I command thee this day, shall be in thine heart: 7 And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up.
Psalm 78:5 For he established a testimony in Jacob, and appointed a law in Israel, which he commanded our fathers, that they should make them known to their children: 6 That the generation to come might know them, even the children which should be born; who should arise and declare them to their children: 7 That they might set their hope in God, and not forget the works of God, but keep his commandments: 8 And might not be as their fathers, a stubborn and rebellious generation; a generation that set not their heart aright, and whose spirit was not stedfast with God.
We must teach our children and the faithful that Jesus is the Christ. (2 Tim 3:15, 2 Tim 2:2)
2 Tim 3:15 And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.
2 Tim 2:2 And the things that thou hast heard of me among many witnesses, the same commit thou to faithful men, who shall be able to teach others also.