It was narrated from 'Aishah that the Messenger of Allah (ﷺ) said:'The best (most pure) food a man consumes is that which he has earned himself, and his child (and his child's wealth) is part of his earnings."
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَعَلِيُّ بْنُ مُحَمَّدٍ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ بْنِ حَبِيبٍ، قَالُوا حَدَّثَنَا أَبُو مُعَاوِيَةَ، حَدَّثَنَا الأَعْمَشُ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتْ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِنَّ أَطْيَبَ مَا أَكَلَ الرَّجُلُ مِنْ كَسْبِهِ وَإِنَّ وَلَدَهُ مِنْ كَسْبِهِ " .
IbnMaja
The Chapters on Business Transactions • Hadith 2137