John is comparing himself to a servant to show how great Jesus is. AT: "I am not even worthy to do the lowly task of removing his shoes" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This metaphor compares John's baptism with water to the future baptism with the Holy Spirit. This means John's baptism only symbolically cleanses people of their sins. The baptism by the Holy Spirit will truly cleanse people of their sins. If possible, use the same word for "baptize" here as you used for John's baptism to keep the comparison between the two. (See: [[rc://en/ta/man/translate/figs-metaphor]])