What does Acts 10:13 mean?

God is explaining to Peter that the message of Jesus is open to all people, including Gentiles, but He's doing it in a very creative way. He has presented Peter with all different types of animals. Some, including reptiles and birds of prey (Acts 11:6), are forbidden by the Mosaic law to be consumed as food (Deuteronomy 14:7–21). At this time, almost all the Jesus-followers are Jews or part-Jews such as Samaritans, and they understand their faith as a natural extension of Judaism—Jesus is the Jewish Messiah, after all. While modern culture sees a distinct separation between Jews and Christians, to Peter there is no such divide. Without a major change in thinking, he's not going to willingly break the Mosaic law.

Food is an appropriate metaphor for the situation because of the importance of sharing meals in the culture. To host someone in a meal was to accept them and accept responsibility for their well-being. For a Jew to eat with a Gentile would have been considered a horrible breach of custom. It would be showing public approval to their lifestyle. When Jesus ate with tax collectors and "sinners," the Pharisees were horrified, even though the sinners were Jews (Mark 2:15–17).

Unbeknownst to Peter, three men are coming to see him. They have been sent by a Roman centurion named Cornelius who wants to know more about the Jewish God he has been faithfully serving (Acts 10:1–8). Peter will have to enter the home of a Gentile and share a meal. God is showing Peter the food is okay to eat and the host is acceptable to host.