The Arabs adopted the Sassanid tax-system, both the land-tax levied on land owners and the poll-tax levied on individuals, called "jizya", a tax levied on non-Muslims (i.e., the "dhimmi"s). In time, this poll-tax came to be used as a means to humble the non-Muslims, and a number of laws and restrictions evolved to emphasize their inferior status. Under the early orthodox caliphs, as long as the non-Muslims paid their taxes and adhered to the "dhimmi" laws, administrators were enjoined to leave non-Muslims "in their religion and their land." (Caliph Abu Bakr, qtd. in ).