John 3: 23-26
“Now John also was baptizing at Aenon near Salim, because there was plenty of water, and people were coming and being baptized. (This was before John was put in prison.) An argument developed between some of John’s disciples and a certain Jew over the matter of ceremonial washing. They came to John and said to him, “Rabbi, that man who was with you on the other side of the Jordan—the one you testified about—look, he is baptizing, and everyone is going to him.’”
To be baptized is a form “ceremonial washing.” To argue over the matter probably means that they were discussing who should be doing it. The Bible does not tell us, but it is not a stretch to imagine that the Jew in the story was claiming that only “authorized” Jews should be performing any kind of ceremonial washing or baptism.