Maimonides the Jewish sage made interesting comments on purification, the mikveh and repentance more than a thousand years after the Good News had been first proclaimed which can be compared to the work of R. John. He wrote,
"Therefore the Sages have said, 'If a man immerses himself, but without special intention, it is as though he has not immersed himself at all.’ Nevertheless we may find some indication (for the moral basis) of this: just as one who sets his heart on becoming clean becomes clean as soon as he has immersed himself, although nothing new has befallen his body, so, too, one who sets his heart on cleansing himself from the uncleannesses that beset men’s souls - namely, wrongful thoughts and false convictions - becomes clean as soon as he consents in his heart to shun those counsels and bring his soul into the waters of pure reason. Behold, Scripture says, 'And I will sprinkle clean water upon you and ye shall be clean; from all your uncleannesses and from all your idols I will cleanse you.’”1
Maimonides, along with R. Akiva, believed the verse in Ezekiel was written with the idea of providing purification, and was comparable with the purification which resulted from immersion in a mikveh.
It is also interesting to note that Maimonides mentioned Ezekiel’s sprinkling in a discussion about the importance of purifying the heart through repentance from wrong thoughts and convictions, together with purification of the body, thus expressing a very similar idea of repentance with the mikveh or sprinkling of water as did R. John in his proclamation of the end-time baptism of repentance for the remission of sins.
Furthermore, Maimonides confirmed the traditional Jewish interpretation of Leviticus 11:36 concerning purification by a spring or a gathering (mikveh) of water. Previous to this discussion of immersion in the mikveh and Ezekiel’s purification in Yad, Mikva’ot 11:12, he contrasted purification by either the water of a spring or the water gathered in the mikveh in Yad, Mikva’ot 9:8,
"Wherein does a spring differ from an immersion pool? An immersion pool imparts cleanness only if it contains forty seah, but a spring imparts cleanness however little its quantity.”2
He goes on to say that someone whose defilement of venereal emission has ceased may immerse in the flowing spring even if it was not forty seah.
Long after the Messianic baptism of repentance for the remission of sins had been proclaimed Maimonides spoke of traditional Jewish baptism in similar terminology showing the common idea in relation to R. John’s baptism and typical Jewish purification.
1Herbert Danby’s translation of Maimonides Book of Cleanness, 11:12 "Mikva’ot” p 535.
2op.cit.