Hadith 5:752
Abu Usama narrated to us, from Hisham, from al-Hasan, who said: For Zakat, there is a known limit. When that time arrives, he calculates his wealth, both that which is present and that which is absent, and he pays [Zakat] on its behalf, except for what is a debt upon him.
حدثنا أبو أسامة عن هشام عن الحسن قال للزكاة حد معلوم فإذا جاء ذلك حسب ماله الشاهد والغائب فيؤدي عنه إلا ما كان من دين عليه