According to Josephus, John the Baptist “commanded the Jews to exercise virtue, both as to righteousness towards one another, and piety towards God, and so to come to baptism; for that the washing [with water] would be acceptable to him, if they made use of it, not in order to the putting away [or the remission] of some sins [only], but for the purification of the body; supposing still that the soul was thoroughly purified beforehand by righteousness.”
His baptism was for the “purification of the body”. Therefore Paula Fredriksen has said that John could be called John the Purifier. The New Testament holds that it was a baptism of repentance for the forgiveness of sins.
Jews could become unclean by touching a dead body, the flow of fluids from the sexual organs, skin diseases, or not keeping kosher food laws. Contact with non-Jews was avoided by the strict because Gentiles ate prohibited foods and their impurity might be contagious.
But it is easy for us to misunderstand the intent of purity for Jews. In fact, it is easy to fall into an unintentional anti-Semitism about it. Some scholars claim that Jesus was mainly about opposing the Jewish purity concept. Purity seems to us a concern that excludes people. Some denominations make inclusion a central principle today. So it makes Jesus relevant if he opposed the exclusive ideology of purity. But the exclusion/inclusion concept is too simple. And Jew equals exclusive while Jesus equals inclusive is both offensive and untrue.
It is helpful to keep in mind Lord Chesterfield’s definition of dirt as matter out of place. The platonic and Gnostic idea that matter is bad has nothing to do with clean and unclean in the Bible. Disorder is what is bad. We might bring in our notion of clutter here. Purity was a way of ordering life. Clean is ordered and unclean is disordered. This is how to understand much of the P (priestly) strand of the Hebrew Bible. When God created the world, he did not so much make something out of nothing as he brought order to existence. I think the priests saw the minute regulations about purity in Leviticus as a further ordering of creation.
In regard to Jesus, the point to remember is that the Temple was still standing when he lived. Purity had to do with who had access to the Temple. It mostly concerned the priests who worked there and worshipers who came there occasionally. This was not trivial. Access to the Temple was access to God, after all. If you were unclean, you couldn’t approach God. But this did not apply so much to home life and village life. (After the destruction of the Temple, purity in Judaism became more a matter of everyday life). And, if you became unclean, it was easy to fix.
The gospels show Jesus touching lepers (Mark 1:41) and a hemorrhaging woman (Mark 5:25). This would have made Jesus ritually unclean. But, as Fredriksen points out, “in his own time and culture . . . Jesus would simply undergo a ritual cleansing himself in order to be purified.” ( Jesus of Nazareth, King of the Jews: A Jewish Life and the Emergence of Christianity p. 200). It would not have been a big deal. It was certainly not the kind of thing that would have gotten him into trouble with the authorities.
There is no good evidence that either John the Baptist or Jesus was in open rebellion against the Jewish purity concept. What they did do, like other prophets before them, was to call people to a much greater concern with moral purity than with ritual purity. Ritual impurity (disorder) could obstruct one’s access to the Temple, but moral impurity (disorder) could bring down the wrath of God.