John 1:25 - Clarke's commentary and critical notes on the Bible

And they asked him, and said unto him, Why baptizest thou then, if thou be not that Christ, nor Elias, neither that prophet? Why baptizest thou then? - Baptism was a very common ceremony among the Jews, who never received a proselyte into the full enjoyment of a Jew's privileges, till he was both baptized and circumcised. But such baptisms were never performed except by an ordinance of the Sanhedrin, or in the presence of three magistrates: besides, they never baptized any Jew or Jewess, nor even those who were the children of their proselytes; for, as all these were considered as born in the covenant, they had no need of baptism, which was used only as an introductory rite. Now, as John had, in this respect, altered the common custom so very essentially, admitting to his baptism the Jews in general, the Sanhedrin took it for granted that no man had authority to make such changes, unless especially commissioned from on high; and that only the prophet, or Elijah, or the Messiah himself; could have authority to act as John did. See the observations at the conclusion of Mark.