What does Acts 10:44 mean?

Peter has just begun to tell a room filled with Gentiles about Jesus' crucifixion, resurrection, and offer of reconciliation with God when the Holy Spirit indwells the listeners. Peter had received a vision two days before, effectively telling him that Jesus had come for the Gentiles, as well (Acts 10:9–16). And Jesus had told him and the other apostles they would be His witnesses to "the end of the earth" (Acts 1:8). But the natural progression, as Peter has seen it, is that he preaches extensively, people affirm their faith, he or another apostle lays hands on them and/or they're baptized, and then the Holy Spirit comes down (Acts 2:37–41; 8:14–17).

This spontaneous falling, before he's even gotten to the meat of his message (Acts 11:15), is unprecedented. It's also a demonstration of how saving faith is truly expressed: by belief and trust, not by physical rituals or prayers.

It's an important event, however, and important that Peter is there to witness it. In Matthew 16:18–19, Jesus says, "And I tell you, you are Peter, and on this rock I will build my church, and the gates of hell shall not prevail against it. I will give you the keys to the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven" (see also John 20:23). Roman Catholics believe Jesus is installing Peter as the first pope, but the "rock" is Peter's confession that Jesus is the Christ (Matthew 16:16), not Peter himself. Still, it is interesting to note that Peter is present at a lot of firsts:

• The first time the Holy Spirit indwells Jesus-followers who had believed in Jesus even before His ascension (Acts 2:1–4).
• The first time the Holy Spirit indwells faithful Jews who come to believe in Jesus after His ascension (Acts 2:37–41).
• The first time the Holy Spirit indwells Samaritans who come to believe in Jesus (Acts 8:14–17).

Peter is not present, apparently, at the first time the Holy Spirit indwells people outside of Jerusalem (Acts 9:31) or the first time a single Gentile God-follower receives the Holy Spirit (Acts 8:26–40). But here he is witnessing another first: the conversion of a group of Gentiles, in fulfilment of Acts 1:8.

The Holy Spirit, Himself, presents the validation of His work among the Gentiles. He causes them to speak in tongues: other earthly languages. Peter will have them baptized and then stay several days to complete their initial training (Acts 10:46–48). When he returns to Jerusalem, he'll have a bigger job: convincing the church leaders of what happened (Acts 11:1–18) and, later, that Gentiles do not need to be full converts to Judaism in order to be Christ-followers (Acts 15:7–9).