He is the one who comes after me, who is preferred before me, whose sandal strap I'm not worthy to loosen."

 The deputation which came to interview John was composed of two kinds of people. First, there were the priests and the Levites. Their interest was very natural, for John was the son of Zacharias, and Zacharias was a priest ( Luke 1:5). In Judaism the only qualification for the priesthood was descent. If a man was not a descendant of Aaron nothing could make him a priest; if he was a descendant of Aaron nothing could stop him being one. Therefore, in the eyes of the authorities John the Baptist was in fact a priest and it was very natural that the priests should come to find out why he was behaving in such an unusual way. Second, there were emissaries of the Pharisees. It may well be that behind them was the Sanhedrin. One of the functions of the Sanhedrin was to deal with any man who was suspected of being a false prophet. John was a preacher to whom the people were flocking in hordes. The Sanhedrin may well have felt it their duty to check up on this man in case he was a false prophet. 