מדרש אויף משלי 1:4

[4] (Proverbs 1:4): 'To give prudence to the simple, etc.' - Solomon said: I was simple, and the Holy One, blessed be He, gave me prudence; I was a youth, and the Holy One, blessed be He, gave me discretion. Alternatively, 'to give prudence to the simple' - from how many years onward does a person need to have prudence? From the age of twenty and above. 'To the young man knowledge and discretion' - until how many years is a person considered a youth? Rabbi Meir says: until 25 years, Rabbi Akiva says: until 30 years. Rabbi Ishmael says: neither according to this opinion nor according to that, but until twenty years, for from twenty years and above his sins are considered against him, as it is said: 'from twenty years and above he will come to work service,' (What is 'service of service'? Resh Lakish says: there is no service except prayer, as it is said (Psalms 2:11): 'Serve the Lord with fear'), from the time he is considered for service - he is considered for transgression.