Hadith 4259
Amarah bin Umair narrates: My paternal aunt had an orphan child under her care. That child used to earn (by working), but the woman considered it a sin to eat anything from his earnings. She asked Lady Aisha (may Allah be pleased with her) about this. So Lady Aisha (may Allah be pleased with her) informed: The Prophet Muhammad (peace be upon him) said: The purest thing is that which a person eats from his own earnings, and a man's children are a part of his earnings.