John the Baptist (who has been imprisoned by Herod, remember) hears the reports of the miracles Jesus has been performing. And then he does something strange, because he seemed to know exactly who Jesus was when he baptized Him. He sends his disciples to ask Jesus if He really is the promised Messiah.
Some historical context is helpful here. At that time, most of the Jews thought the Messiah was going to raise an army to expel the Roman invaders, restore the kingdom of Israel, and sit on the throne of his father David to rule like he did. Except for defeating the Romans, Jesus is going to rule over the nations like that…eventually. This may not have been John’s view, though, because he had been preaching to encourage the people to repent because judgement was coming. Perhaps he thought Jesus had come to bring about the judgement of God upon sinful humanity and was wondering when He’d get on with it. And Jesus is going to do that…eventually.
Verse 21 tells us that in the same hour that John’s disciples asked Jesus their question, Jesus healed many people of various afflictions. Jesus says to them to tell John what they have seen and heard, because they were certainly witness to these things. The words He uses are allusions to passages in Isaiah that talk of the restoration of Israel. So Jesus is saying to them “I am the One you are waiting for; see the deeds I am here to do.”
We look forward to Your return, King Jesus. Make us ready to receive You.