It is narrated from Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: "The purest thing a man eats is from his own earnings, and his child is from his earnings." Ya'la bin Ubayd likewise narrated it from al-A'mash.
It has also been narrated from Matar, from al-Hakam, from Ibrahim, from Shurayh, from Aishah (may Allah be pleased with her), from the Prophet (peace and blessings be upon him), but that is not preserved (ghayr mahfuz).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15747