Why did Pope Francis pray at the wall?

(CNN) -- "Something there is that doesn't love a wall," wrote Robert Frost. This something is someone now: Pope Francis.

In a strong, apparently unscripted move on his recent visit to Bethlehem, the birthplace of Jesus, on Sunday the pontiff suddenly waved to the driver of his Popemobile, asking to get out. Surrounded by guards and by children waving Palestinian flags, he got out, walked over to the wall that separates Israel from its Palestinian neighbors, and he did something remarkably simple but with astonishing power: He prayed.

 Pope Francis touches the wall that divides Israel from the West Bank, on his way to celebrate a mass in Manger Square next to the Church of the Nativity in Bethlehem

This symbolic gesture occurred at a well-known portion of the wall, a segment covered with graffiti. Somebody had spray-painted a message in black: "Pope we need some 1 to speak about justice Bethlehem look like Warsaw ghetto."

In bold red letters the Pope could read: "Free Palestine." While Israeli guards looked anxiously down from a nearby tower, wondering what on Earth was going on, Francis touched the wall with his right hand, bent his head, and prayed for several minutes. Afterward, he kissed the wall, then walked slowly back to his vehicle.