John was in a very disappointing and discouraging position. He had given his every effort and to prepare the way for the Messiah and then, because of his integrity in the face of a dissolute and narcissistic Herod, was thrown into prison.
As far as we know, Jesus never visited John in prison and it is not hard to imagine how John could have begun to loose heart - was his life work all for nothing?
John sent some of his disciples to enquire of Jesus and Jesus replied as recorded in Matt 11:1-5. Jesus concludes his reply message to John in the gentlest rebuke ever recorded - a blessing. Ellicott expresses it this way:
Blessed is he.--The words at once confirm the view that the question
which the messengers had brought came from the Baptist himself, and
show how tenderly our Lord dealt with the impatience which it implied.
A warning was needed, but it was given in the form of a beatitude
which it was still open to him to claim and make his own. Not to find
a stumbling-block in the manner in which the Christ had actually come,
that was the condition of entering fully into the blessedness of His
The Pulpit commentary is even more succinct and pointed:
And blessed is he, whosoever shall not be offended (Matthew 5:29,
note) in me; shall find none occasion of stumbling in me (Revised
Version). But exhibits perfect trust under delay and disappointment