Sahih Bukhari
Obligatory Charity Tax (Zakat)
Volume: 002 / Book Number: 024 / Hadith Number: 531
Narrated Anas:
Abu Bakr wrote to me what Allah's Apostle has made compulsory (regarding Zakat) and this was mentioned in it: If a property is equally owned by two partners, they should pay the combined Zakat and it will be considered that both of them have paid their Zakat equally.