Quite a few 'Islamic' laws derived from preexisting Roman and Persian laws, including the jizya:
As a matter of fact, Jizya or poll tax had been in vogue since before the advent of Islam. The Greeks are reported to have imposed a similar tax upon the inhabitants of the coastal regions of Asia Minor during 500 B.C. The Romans imposed similar taxes upon the people they conquered, and the amount was much heavier than what was later imposed by the Muslims. The Persians are also reported to have introduced a similar tax upon their subjects.6 According to Shibli Nu'mani, theword Jizya itself is the Arabicised version of the word c*c^ (Kizyat), meaning a levy which the Persian rulers used to employ in administering the affairs of war. Shibli further indicates that this term was either in currency in both the languages, or the Arabs adapted it from the Persian language.
Whatever the case, it is certain that the Arabs first knew about this tax from the Persians. The Sasanid emperor Nawsherwan is reported to have introduced a tax, upon his subjects also termed as Jizya by the Arab historians, with the exemption of the nobility, satraps, military personnel, secretaries and those in the service of the emperor, at the varying rates of 12/8/6/2 dirhams upon each person.