He’s feeling his oats.
More Traditional Proverbs:
Seek peacefully, you will find.Traditional
She's a nut.
Traditional
A fine beer may be judged with only one sip, but it's better to be thoroughly sure.
Traditional
As you climb the ladder of success, check occasionally to make sure it is leaning against the right wall.
Traditional
A man can't be judge of his neighbor's intelligence. His own vital experience is never his neighbor's.
Traditional
My barn having burned to the ground, I can now see the moon
Traditional