Matthew 3:11. He that cometh after me is mightier than I, whose shoes I am not worthy to bear.
To carry the master’s sandals was considered the most menial duty that could be performed. On entering a house the sandals are taken off by a servant, who takes care of them, and brings them again when needed. In India it is customary for a servant to accompany his master when he walks out. If the master desires to walk barefoot on the soft grass or the smooth ground the servant removes the sandals and carries them in his hand. John felt himself unworthy to do for Christ even the meanest work of a servant.
See also note on John 1:27 (#791).