Musannaf Ibn Abi Shaybah 27523 — A man who writes: Amma ba'd

Zayd bin Aslam said: My father sent me to Sayyiduna Ibn Umar (may Allah be pleased with them both), and I saw him writing a letter, and he wrote: 'Bismillahir-Rahmanir-Rahim, amma ba'd' (In the name of Allah, the Most Gracious, the Most Merciful; to proceed).