John was contrasting how he was purifying people with water with how the one to come would purify people with the Holy Spirit. To baptize with the Holy Spirit is a metaphor meaning that that person would send the Holy Spirit to purify people. The Holy Spirit would then live in them and empower them to stop sinning and to obey God. If possible, use the same word for "baptize" here as you used for John's baptism. (See: [[rc://en/ta/man/jit/figs-metaphor]])