Musannaf Ibn Abi Shaybah 10890 — The Christians of Banu Taghlib: what

It is narrated from Abu Mijlaz that Sayyiduna Umar (may Allah be pleased with him) sent Sayyiduna Uthman bin Hunayf (may Allah be pleased with him) (to collect the tithes and the like). He fixed one dirham on every twenty dirhams on the wealth of the dhimmis who travelled with it to other cities and traded, and he wrote this to Sayyiduna Umar. He approved of it and permitted it. Then he said to Sayyiduna Umar: What do you order us to take from the traders of the people of war? He said: When you go to their cities, how much do they take from you? People said: A tenth. He said: Then take the same from them.