Origins of baptism

Hobbes again ( Leviathan 41) on the Mosaic predecessors to Christian baptism:

“As the children of Israel had for a sacrament of their reception into the kingdom of God, before the time of Moses, the rite of circumcision, which rite, having been omitted in the wilderness, was again restored as soon as they came into the Land of Promise; so also the Jews, before the coming of our Saviour, had a rite of baptizing, that is, of washing all those that, being Gentiles, embraces the God of Israel. This rite St. John the Baptist used in the reception of all them that gave their names to the Christ, whom he preached to be already come into the world; and our Saviour instituted the same for a sacrament to be taken by all that believed in him. For what cause the rite of baptism first proceeded is not expressed formally in the Scripture, but it may be probably thought to be an imitation of the law of Moses concerning leprosy; wherein the leprous man was commanded to be kept out of the camp of Israel for a certain time; after which time, being judged by the priest to be clean, he was admitted into the camp after a solemn washing. And this may therefore be a type of the washing in baptism, wherein such men as are cleansed of the leprosy of sin by faith are received into the Church with the solemnity of baptism.”