IN THE OLD TESTAMENT:
Baptism of Purification. Old Testament washings were almost always for those of the already believing community. They symbolized cleansing from sin and guilt. Whereas sacrifices were to atone for acts of sin, washing or bathing seems generally associate with cleansing form, a sinful or otherwise unholy condition.
(National) Exodus 19:10-11 Before God spoke to the Israelites from Sinai; he commanded them to consecrate themselves, their clothes and be ready by the 3rd day, when He would appear to them.
(Priestly) Leviticus 8:6-9: At the consecration of the priests, Moses brought Aaron and his sons forward and washed them with water.
(Individual) Leviticus 14:8-9 A person who had recovered from an unclean skin disease had to wash his clothes, shave off all of his hair and bathe with water to be ceremonially clean.
INTERTESTIMENTAL AND RABBINIC JUDAISM:
Baptism of Purification. The Jewish community at Qumran (probably an Essene group ca. 2nd century B.C. – 1 st century A.D. that produced the Dead Sea Scrolls). Used washing as a rite of cleaning. From the Damascus Rule (translation from The Dead Sea Scrolls in English, Gez Vermes, tr.):
“No man shall bathe in dirty water or in an amount too shallow to cover a man. He shall not purify himself with water contained in a vessel” (From chapter 10).
“No man entering the house of worship shall come unclean and in need of washing” (from chapter 11).
Baptism of Initiation: In rabbinic and earlier forms of Judaism, baptism (along with male circumcision and sacrificial offerings) was a requirement for full conversion. The dating of this practice is somewhat obscure, but it postdates the Old Testament and predates the Mishnah. The Soncino Talmud states:
“As your forefathers entered into the Covenant only by circumcision, immersion and the sprinkling of the blood, so shall they (the proselytes) enter the Covenant only by circumcision, immersion, and sprinkling of the blood” (Keritot 9a).
Baptism of Purification: After the destruction of the Temple in 70 A.D., the biblical purification laws (see above, Old Testament) were confined to the purification of the niddah, the ritually unclean woman discussed in such passages as Leviticus 12:1-8 and 15:19-24.
The Jewish mikveh (immersion or t’vilah in a ritual bath) embraces both of the categories of purification and initiation and is practiced among Orthodox Jews to this day.