John uses the image of carrying Jesus’ sandals to show that, in relationship to Jesus, he is even less than a heathen slave. John presents Jesus as both royal (see Matthew 3:3) and infinitely more powerful than John himself. John’s analogy may have been prompted by seeing real slaves there.
Untying someone’s shoes and carrying them around was considered to be such a humiliating task that it was not expected even of Jewish slaves, but only of foreign slaves. By employing this image, John conveys the idea that he is, in terms of his relationship to Jesus, worth even less than a heathen slave.1
In the kingdom of heaven Jesus accomplishes so much more than John does. Jesus is presented by John in terms of his Lordship, in accordance with the prophecy mentioned in Matthew 3:3, which speaks of his royalty. John is not worthy of carrying the shoes of the Messiah, that is, he is unworthy of even conducting slave labour for him. This is how great the chasm is between the two of them. It is not impossible that John specifically chose this example at the time because those prominent figures in Judea who had come to John to be baptized had brought slaves along with them for the very purpose of holding and carrying their shoes when they entered the water.2
11 Moi, je vous baptise d'eau, pour vous amener à la repentance; mais celui qui vient après moi est plus puissant que moi, et je ne suis pas digne de porter ses souliers. Lui, il vous baptisera du Saint-Esprit et de feu.