Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) the like of the document about zakah that was found in the hilt of the sword of Sayyiduna Umar (may Allah be pleased with him), up to the zakah of silver, and in it is: "Between the two dues there are twenty dirhams or two goats worth ten dirhams each."
In the narration of al-Mashshat (the chain is) from al-Muthanna bin Anas, from his father, from Anas bin Malik, and this is more likely, for he is al-Muthanna bin Abdullah bin Anas, attributed to his grandfather. We have narrated this hadith from the hadith of Thumamah bin Abdullah bin Anas from Anas through authentic routes, and we have narrated it from Salim and Nafi' both connected (mawsul) and mursal, and from the hadith of Amr bin Hazm connected; all of these strengthen one another. And success is from Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7256