Sunan an-Nasa'i 4452

أَخْبَرَنَا أَحْمَدُ بْنُ حَفْصِ بْنِ عَبْدِ اللَّهِ النَّيْسَابُورِيُّ، قَالَ حَدَّثَنِي أَبِي قَالَ، حَدَّثَنِي إِبْرَاهِيمُ بْنُ طَهْمَانَ، عَنْ عُمَرَ بْنِ سَعِيدٍ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتْ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ إِنَّ أَطْيَبَ مَا أَكَلَ الرَّجُلُ مِنْ كَسْبِهِ وَإِنَّ وَلَدَهُ 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

Reference

Sunan an-Nasa'i 4452

In-book

Book 44, Hadith 4