Sahih Bukhari · Hadith 3106
One-fifth of Booty to the Cause of Allah (Khumus) - كتاب فرض الخمس
حدثنا محمد بن عبد الله الأنصاري، قال حدثني أبي، عن ثمامة، عن أنس، أن أبا بكر رضى الله عنه لما استخلف بعثه إلى البحرين، وكتب له هذا الكتاب وختمه، وكان نقش الخاتم ثلاثة أسطر محمد سطر، ورسول سطر، والله سطر.
Narrated Anas: That when Abu Bakr became the Caliph, he sent him to Bahrain and wrote this letter for him, and stamped it with the Ring of the Prophet. Three lines were engraved on the Ring, (the word) 'Muhammad' was in a line, 'Apostle' was in another line, and 'Allah' in a third.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).