21 When Enoch was 65 years old, he became the father of Methuselah. 22 And after he had become the father of Methuselah,
Enoch walked with God 300 years and had other sons and daughters. 23So
Enoch lived a total of 365 years. 24 Enoch walked with God, and
then he was no more, because God had taken him away.
To this record must be added two more texts about Enoch:
Heb 11:5 - By faith Enoch was translated not to see death, and he was not found, because God had taken him up. For before the translation, he was commended to have pleased God. [The text of LXX in Gen 5:22 has "well-pleasing to God ..."]
Jude 14 - And Enoch, the seventh from Adam, also prophesied as to these, saying: "Behold, the Lord has come amidst myriads of His holy ones
Thus, it appears that Enoch was called to a be a prophet of God after the birth of his first son. Just why God chose this timing is not stated. However, here are some suggestions:
This was God's sovereign will
Enoch, following the birth of his son, Methuselah, re-dedicated himself to serving God
God waited until after the birth of Methuselah so that Enoch would better understand the coming and birth of Messiah
Thus, there is nothing here to suggest that before the birth of Methuselah, Enoch was wicked or needed drastic reform. All that is stated is a greater dedication and closeness to God at that point in his life.
First, it is clear that the statement "after he had become the father of Methuselah, Enoch walked with God" does not imply that "after he had become the father of Methuselah, Enoch started to walk with God". He may have already walked with God before.
Having said that, if the name Methuselah really means "death and sent", or "he dies, and the sending forth", or "when he dies, there shall be a sending forth" , then we can safely hypothesize that, no later than at Methuselah's birth, Enoch received the revelation that God would punish mankind's wickedness by sending forth a flood after the death of his firstborn son. (Otherwise, why would Enoch give such a name to his son?) In that case, it is sound to further hypothetize that such revelation motivated Enoch to walk with God even more closely than before.
Jasher 3:1 “Enoch lived sixty-five years and he had Methuselah; and Enoch walked with God after having a son, Methuselah, and he served the Lord,and despised the evil ways of men.”
Jasher 3:10 “They assembled in all, one hundred and thirty kings and princes, and they made Enoch king over them and they were all under his power and command.”
Jasher 3:12 “Enoch reigned over the sons of men two hundred and forty-three years, and he did justice and righteousness with all his people, and he led them in the ways of the Lord.”
Jasher 3:23 … an angel of the Lord then called to Enoch from heaven, and wished to bring him up to heaven to make him reign there over the sons of God, as he had reigned over the sons of men on earth.”
Jasher 3:36 … Enoch ascended into heaven in a whirlwind, with horses and chariots of fire.”