Sahih al-Bukhari 1450
Sahih al-Bukhari · Book 24: Obligatory Charity Tax (Zakat) · The individual property of different people should neither be gathered together nor the joint property should be divided, in assessing the Zakat
Narrated Anas:
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الأَنْصَارِيُّ ، قَالَ حَدَّثَنِي أَبِي قَالَ، حَدَّثَنِي ثُمَامَةُ ، أَنَّ أَنَسًا ـ رضى الله عنه ـ حَدَّثَهُ أَنَّ أَبَا بَكْرٍ ـ رضى الله عنه ـ كَتَبَ لَهُ الَّتِي فَرَضَ رَسُولُ اللَّهِ صلى الله عليه وسلم " وَلاَ يُجْمَعُ بَيْنَ مُتَفَرِّقٍ، وَلاَ يُفَرَّقُ بَيْنَ مُجْتَمِعٍ، خَشْيَةَ الصَّدَقَةِ " .
Abu Bakr wrote to me what was made compulsory by Allah's Messenger (ﷺ) and that was (regarding the payments of Zakat): Neither the property of different people may be taken together nor the joint property may be split for fear of (paying more, or receiving less) Zakat.