Sunan an-Nasa'i 4451
It was narrated that 'Aishah said:
"The Messenger of Allah said: 'The best (most pure) food that a man eats is that which he has earned himself, and his child (and his child's wealth) is part of his earning,"
أَخْبَرَنَا يُوسُفُ بْنُ عِيسَى، قَالَ أَنْبَأَنَا الْفَضْلُ بْنُ مُوسَى، قَالَ أَنْبَأَنَا الأَعْمَشُ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ إِنَّ أَطْيَبَ مَا أَكَلَ الرَّجُلُ مِنْ كَسْبِهِ وَوَلَدُهُ مِنْ كَسْبِهِ ‏"‏ ‏.‏