In the Mishnah's taxonomy, the commandments are bisected into zeman gerama and en ha-zeman gerama. The first of these terms is understood by the Talmud as time-bound or intermittent, and the second as applicable at all times or perennial. What is the origin of this classification? Scripture is never invoked; nor, for that matter, is halakhah le-moshe mi-sinai. Moreover, according to Maimonides, traditions of Moses from Sinai are immune to dispute. This Maimonidean litmus test, though inadequate to identify Sinaitic material, helps eliminate non-Sinaitic. If Sifre Numbers is to be believed, classifying miṣvot into zeman gerama and en ha-zeman gerama was not the consensus. Rather was it a classification peculiar to the tanna R. Simeon.

But whether broadly or narrowly subscribed to, the zeman gerama taxonomy seems totally arbitrary, and not even Sifre dispels the sense of arbitrariness. Why should so improbable a yardstick distinguish men's miṣvot from all-Israelite ones? Amazingly, only a handful of writers volunteer solutions to this conundrum. Among the handful, four approaches are discernible. These may be dubbed: the Maimonidean, the Abudrahamian, the apologetic and the dogmatic.