Anas bin Sirin (may Allah have mercy on him) said: Anas bin Malik (may Allah be pleased with him) sent me a message, but I delayed; at the second message I came. Anas bin Malik (may Allah be pleased with him) said: I thought that if I had told you, for my pleasure, to move this stone, you would have done it. But I chose the best of work for you, and you disliked it. He said: I will write out for you the practice of Sayyiduna Umar (may Allah be pleased with him). I said: Write it. So he wrote that from the Muslims one dirham is to be collected from every forty dirhams; from the dhimmis, one dirham from every twenty dirhams; and from those who have no covenant of protection, one dirham from every ten dirhams. I asked: Who are the non-dhimmis? He said: The Romans who come to Syria for trade.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18764