Musnad Ahmad 1153:934

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from al-Hakam, from 'Umarah ibn 'Umayr, from his mother, from 'Aishah, from the Prophet, peace and blessings of Allah be upon him, that he said: "A man's child is from his earnings, from the purest of his earnings. So eat from their wealth, in good health (and enjoyment)."