The entirety of chapter 10 is about Cornelius and Peter, and the preaching of the Gospel to Gentiles through Peter. Though it’s narrow in scope, it is a deep pool of wisdom for us.
10:1 Caesarea is north of Joppa along the coast, up closer to Nazareth than Jerusalem (see the second map from the Acts 9 notes). A centurion is a Roman soldier in charge of 100 soldiers. A cohort was a group of about 600 soldiers, so Cornelius would have been one of six centurions of this cohort. (There were 10 cohorts, so about 6,000 soldiers, in a Roman legion.)
10:2 Luke calls this man “devout”. He and his household (which would have included not only his family but also servants, household managers, etc.) were evidently Jewish converts, awaiting the Messiah.
10:3-9 The ninth hour is about 3pm, one of the hours of prayer. An angel (the text doesn’t say “the” angel of God, which is often a reference in other places, especially in the Old Testament, to an appearance of Jesus specifically) appears to Cornelius to let him know that his prayers are accepted by God, and that he should send for a man named Simon Peter to come to him. Notice that Cornelius chooses a “devout” soldier to go for him. The combination of Roman soldiers and devoutness seems to us to be odd, given the picture we have of the Romans from the Gospel accounts and other historical witnesses about things like the destruction of Jerusalem in 70 AD. Dare we say, “not all Romans”?
10:9-16 Just as Cornelius is given a vision, so too is Peter. Peter’s is at first cryptic to him; he doesn’t understand it. It’s only later, as the story unfolds and he talks with Cornelius that the meaning of it becomes clear.
10:14-15 A note on “common” or “unclean”...the background of this is the Jewish dietary laws. In places such as Leviticus 11 God prescribes what sorts of animals would be considered clean, or acceptable to eat, and which would be unclean. The idea of “common” is set against what is “set apart” or “holy” (e.g. Leviticus 20:25). Again it is God who defines this for Israel. God set apart some animals for food for Israel and declared them clean; Peter has been diligent about following this. But now, God declares something new (though, again, the meaning of it comes later on in the chapter; right now we are being told what happened).
It must be noted, however, that Peter is staying at the home of another Simon, whom Luke has told us twice so far is a “tanner” (9:43, 10:6). What does a tanner do? Tans the hides of dead animals! He would be therefore ceremonially unclean for being in contact with them, even if the animals themselves would be ceremonially clean. It’s a fascinating little detail that means more than it seems, as Peter is on this physical and spiritual journey towards a new thing that God is doing.
At the same time, Peter’s response to the voice is emphatic; we might say “there’s no way!” And he does it three times! Peter stands on his conviction on religious principle, but God is up to something new, and Peter doesn’t immediately recognize that.
10:16-27 In addition to the travel narrative that brings Peter from Joppa to Cornelius’ home in Caesarea, we have the note that it is the Spirit who directly prompts Peter to go with them. Without this, he may have been reluctant since (as we’ll hear in 10:28-29) Jews were not to associate with non-Jews, particularly in the home. Entering Cornelius’ house would have, from a Jewish perspective, rendered Peter ceremonially unclean.
10:28-29 Peter now reveals that he understands the vision, though he’ll expand on it more fully once he learns more from Cornelius.
10:30-33 Cornelius has gathered many people, expecting a word from God through Peter. He truly was devout!
10:34-43 Peter preaches what all preachers should: Jesus Christ and Him crucified and risen for the forgiveness of sins. Though it’s the same message, he’s now preaching with a new understanding: that this Gospel of Jesus isn’t just for Israel but for all people (10:34-35, and 10:36). Peter understands that the vision he received is not just about food (it is about food, but not only about food) but also about people. The Jewish understanding was that they were the holy and clean people before God, and others were common and unclean. But now, through Jesus, all people can be included in that category of holy and clean before God.
10:44-48 The result of preaching is the outpouring of the Holy Spirit, which then is accompanied immediately by Baptism.
Some have pointed to this example as evidence that all Christians should experience things like speaking in tongues as evidence of having the Spirit. But in context of the whole Scriptures (particularly in places like 1 Corinthians 12-14, as well as the amazement of the Jews that the Gentiles are now included - see 10:45-46 and 11:17-18), it’s evident that speaking in tongues in Acts 2 and here in Acts 10 carried the specific purpose of fulfilling God’s promise (as quoted by Peter on the day of Pentecost from Joel 2) to pour out His Spirit on “all flesh”. That includes Gentiles as well as Jews. And so it’s best to think of this episode as “the day of Gentile Pentecost” rather than a “new normal” for all Christians.
10:48 Christian fellowship—which now supercedes Jewish fellowship—is now demonstrated not only theologically but in the fruit of hospitality, as Peter is invited to stay for several days, and he does. For a Jewish person to even enter a non-Jew’s home renders him unclean, but now he stays for days with them.