So the Roman Captain is minding his own business going about his day when an angel of the Lord appears to him. The command is to beacon Peter to come. Peter a day later has a vision from God about what is acceptable and what is not. Peter thinks he knows the mind of God on such things until God challenges him to broaden his understanding.
Peter is clear that as a fisherman, a disciple of Jesus, and even now has never eaten anything considered unclean by the Jewish law. When God says kill and eat, Peter objects because they are unclean animals. God asks Peter if he will listen to God, or if he will listen to ritual and rule. Not an easy question. This is so much more than simply a question of what is for dinner.
We as humanity are really good at determining what it appropriate and what is not. Those in the world of the church have gotten it down to a science in terms of this is what the Lord says. Peter found himself in that very place, only he was pitting his understanding of the law and teachings of God, against God. The tradition and ritual were deeply rooted in what was given to the people, Israel, thousands of years before. So had God changed? No, the way people followed God had changed. People showed their devotion to God by obeying the law set forth through Moses. Now humanity showed their devotion to God by following the teachings and life of Jesus.
As we look at Jesus all the deeply held rules and rituals were challenged. Jesus ate with unclean people. The line between acceptable and not was clearly blurred by Jesus. Peter was being reminded by God that the possibilities are far greater than ever imagined. The boundaries drawn by human hands are not the ones God draws. Keeping our lives in tune with God will allow us to more clearly hear what God is calling us to. We should listen to God more than we listen to the rituals and laws of the church. This is dangerous and many have used this kind of reasoning to pervert the Gospel in profound ways. This is why community matters. A community will all us to test what it is we are thinking and feeling. If it is what God is calling, we will more than likely not be the only ones who are hearing, if others are listening for God as well.