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 ‏"‏ ‏.‏

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," Translation Not Available

Book Ref: Sunan An Nisai Book 44 Hadith 4451
Web Ref:  Sunan An Nisai Vol 5 Book 44 Hadith 4456