What does Acts 11:16 mean?

Peter is defending his decision to eat with Gentiles. He explains that he'd been invited to tell them about Jesus, when suddenly the Holy Spirit came upon them. It's as if Peter is saying, "It wasn't me! I didn't baptize them or lay hands on them—the Holy Spirit just showed up!"

Whether correctly or not, Peter assumed the Gentiles knew of John's baptism (Acts 10:37). John's baptism was a call to repent of one's sins and choose to follow God. John's ministry was extremely popular; Apollos knew of it (Acts 18:24–28) as did twelve men in Ephesus (Acts 19:1–7). Judaism was a single religion with several different sects and many teachers within those sects. When a person accepted the teachings of a sect—such as the Pharisees, Sadducees, or Essenes—or found a teacher they felt convicted to follow, they would be baptized by being submerged in water.

The Greek baptizō means "to be submerged in water," but it is also used to refer to "being overwhelmed." While John convicted his audience to repent from their sins, he also mentioned that although he baptized with water, the Messiah was coming and would baptize His followers with the fire of the Holy Spirit (Luke 3:16). Jesus reiterated this to the disciples after the resurrection (Acts 1:5), and the Holy Spirit came, with tongues of fire, on Pentecost (Acts 2:1–4). Fire can represent a sacrifice consumed by flames to God (Leviticus 9:24; Romans 12:1) or God's purifying work that removes our sins (1 Peter 1:7).

The Gentiles received the baptism of the Holy Spirit before Peter had laid hands on them or baptized them in water (Acts 10:44). God chooses whom He will save and, as Peter says next, "Who was I that I could stand in God's way?" (Acts 11:17).