Abu Bakr, may Allah be pleased with him, wrote out for him the obligatory rules of zakat that the Messenger of Allah ﷺ had prescribed. It stated, "When there are two partners sharing livestock, they must settle accounts between themselves equitably."
أن أبا بكر رضي الله تعالي عنه كتب له فريضة الصدقة التي فرض رسول الله ﷺ قال: وما كان من خليطين فإنهما يتراجعان بينهما بالسوية.
Bukhari reported it in the Book of Partnership (2487) from Muhammad bin Abdullah bin Muthanna, who said, Thumama bin Abdullah bin Anas told me that Anas had told him, and he narrated it, as mentioned here, in abbreviated form. It has already been mentioned in full in the chapter on zakat.