Proverbs 10:1: a wise son brings joy to his father, but a foolish son brings grief to whom?

Answer: His mother

Proverbs 10:1 opens a new section, "The proverbs of Solomon," with this contrast between a wise son and a foolish one.

“The proverbs of Solomon: A wise son brings joy to his father, but a foolish son grief to his mother.”— Proverbs 10:1 (BSB)