Musannaf Ibn Abi Shaybah 27518 — A man who writes: Amma ba'd

Abu Qilabah said: One who read the letter of Sayyiduna Uthman (may Allah be pleased with him), or to whom the letter of Sayyiduna Uthman was read, related to me that he had written in this way: "Amma ba'd (to proceed)."