From Sahih Bukhari (Hadith 1450):
Narrated Anas: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
Reference: Bukhari 1450