Zur'ah bin Sayf bin Dhi Yazan (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) wrote me a letter in which it was stated: "Whoever remains upon Judaism or Christianity shall not be made to change it; rather, upon them is the jizyah: upon every adult, male or female, free or slave, is one dinar or its equivalent in Ma'afiri cloth."
Among the narrators of this narration are some who are unknown, and no hadith is established by the like of it among the people of knowledge. So whatever in its wording, and in the wording of what preceded it, agrees with the narration of Masruq is acted upon, and whatever goes beyond it must be suspended; and success is from Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18676