John the Baptist's word here does not mean that he was in doubt concerning Christ. He questioned Christ in this way in order to provoke Him to deliver him. He knew that Christ was the Coming One, and he had strongly recommended Him to the people (John 1:26-36). After that, John was put into prison (Matt. 4:12), where he waited, expecting that Christ would do something to deliver him. However, Christ did nothing for him, although He did much to help others. When John heard of this, it might have been that he was about to be stumbled (v. 6). Hence, he sent his disciples with such a question to provoke Christ.