Ephesians 2:3 says " Behold, I was brought forth in iniquity, And in sin my mother conceived me"
If you're old ,young or if you're in your mother's womb, we are all sinners and therefore should always ask for forgiveness of our sins so that God can cleanse us from our sins. Here are few bible verses that talks about sin:
1 John 1:9 "If we confess our sins, he is faithful and just to forgive us [our] sins, and to cleanse us from all unrighteousness"