In Acts 10 beginning at verse-9 we have Luke’s record of Peter’s vision of unclean animals, which the Lord told him to eat (Acts 10:13) and his ultimate preaching of the Gospel to Cornelius, a gentile and Roman Centurion (verse-34 and following). This event occurred probably in the spring or summer of 40 CE during the peace believers experienced while Rome and Jerusalem were on the brink of war over Caligula’s intention of placing a statue of himself within the Temple compound at Jerusalem.
One has to wonder at this point why Jerusalem was so reluctant to preach the Gospel to Rome. Presumably the church authorities there had accepted the idea of the Gospel going to gentile descendents of Shem (Acts 8:4-25) and Ham (Acts 8:26-39). Why were they hesitant about preaching to Rome and Greece? One could point out that the Samaritans and the Ethiopian eunuch already obeyed the Law of Moses, including the ritual of circumcision and the dietary laws, and this could be a valid argument.
Peter relates his vision of unclean animals with accepting the whole gentile community as they were in his day, even those who didn’t practice circumcision (Acts 10:15, 28). The vision he was given was of the three main classes of animals: wild beasts, creeping things and fowls (Acts 10:12), which relates to the three main races descending from Shem, Ham and Japheth (Genesis 10:1. Moreover, we find that Jesus often referred to men, especially unbelievers, as unclean animals (viz. Luke 13:31-32; Matthew 7:15; 12:24, 34: 23:29-33; 24:28). However, in Peter’s vision he is told to “kill and eat” or, in other words, do that which the Law of Moses claimed was ceremonially unclean, and no ceremonially unclean person was permitted to sacrifice/worship before the Lord (Leviticus 7:19-21; cp. Isaiah 52:1). Nevertheless, we see that Peter had modified his understanding of these Scriptures by staying in the home of Simon, the tanner, and eating there as his guest (Acts 10:10). The occupation of tanning was considered unclean by first century Jews. It seems, however, that Peter believed anyone who is cleansed by the blood of Jesus is clean, and nothing, like his legitimate occupation, can make him unclean. Therefore, Peter’s faith was growing, but he needed to go further, hence this vision from the Lord.
Some see a similarity between Peter and the prophet Jonah. Peter’s father’s name was Jonah (Matthew 16:17; John 1:42). Both men seemed hesitant about preaching to gentiles (cp. Jonah 1:1-3). Both men departed from Joppa and preached to gentiles: Jonah to those at Nineveh and Peter to Cornelius at Caesarea, and both needed a special miracle or vision to encourage them to obey the Lord. Yet, if this similarity is valid, this is where the similarity ends. Jonah regretted his success and knew the Lord’s mercy would save the very people who would later destroy his nation (Jonah 4:2), but Peter, knowing that the Roman armies were destined to destroy both Jerusalem and the Temple (cp. Daniel 9:26 and Luke 21:6, 20, 24), not only obeyed the Lord by travelling to Caesarea with Cornelius’ emissaries, but then willingly preached the Gospel to Romans, the descendents of Japheth, and later defended his doing so before those who called his activity into question under the grounds of the Law of Moses (cp. Acts 11:1-18). This is the difference that the presence of the Holy Spirit makes when he dwells within us. The Law can only change our behavior, but God is able to change our hearts.