Jesus lived in Galilee, which was a region in northern Israel. To get to Jerusalem and celebrate the Passover he would need to travel south into what was known as Judea. The typical route would take people through the town of Jericho. It was here that a blind man is sitting by the road and hears that Jesus is passing by. He cries out to him, "Son of David, have pity on me!" The crowd that is travelling with Jesus tells the man to be quiet. Why? I think the reason is that the blind man has used the term "son of David." The Messiah was supposed to be descended from the line of King David, and was often called "the son of David." So for someone to call Jesus this meant that they were saying that he was the Messiah, the rightful king of Israel. The problem is that calling someone the Messiah in public is to invite trouble from the Roman rulers, who would see this as a challenge to their authority. But the blind man doesn't care what the crowd says. He just calls out louder, "Son of David, have pity on me!"
What's interesting is what happens next. Jesus stops and tells them to bring the blind man to him, which they do. He then asks the man what he can do for him, and the blind man asks him to restore his sight, which Jesus does. The healed man rejoices and follows Jesus, along with the rest of the crowd.
It is important to notice that this is the first time that Jesus has made any sort of public acknowledgment that he is the Messiah. He did it in private with his disciples. But not in public. We are not told whether the crowd already believed he was the Messiah, or whether they were surprised by Jesus' acknowledgement. But either way, the fact that Jesus thinks he is the Messiah is now "out." And it is significant that it took a blind man to see it.