What we know about ritual immersion in the late Second Temple period derives mainly from archaeological digs, the Dead Sea Scrolls and rabbinic literature. The archaeological remains of mikvaot (ritual immersion pools; singular: mikveh) and the Dead Sea Scrolls date precisely from this period; whereas, the data coming from rabbinic literature, primarily from the Mishnah and Sifra, have been preserved in texts compiled and edited 150 years after the destruction of the Second Temple. Despite the gap in time between the close of the Second Temple period in 70 C.E. and the completion of the Mishnah and Sifra at approximately 250 C.E., these early rabbinic texts contain information that dovetails remarkably with the archaeological record, and therefore, is relevant for studying ritual immersion in the late Second Temple period.
In the tractate Mikvaot, one of the tractates of the Mishnah, and in Parashah Metsora and Parashah Shemini, two sections of Sifra, the rabbis recorded highlights of their discussions resolving various problems concerning ritual immersion. From their discussions we learn five requirements for a ritually proper mikveh: