What God has made clean, you are not to call profane. One of the many hurdles the young Christian community had to overcome was carrying out the command of Jesus of making disciples of all nations (cf. Matthew 28:19). Christianity was born among the Jewish people, a people who were already steeped in an idea of God (and religion for that matter) that was much similar to the one the followers of Jesus were trying to propagate. As such, it was going to be easy to make disciples from the immediate Jewish community because they were already familiar with the demands of a monotheistic religion. As a matter of fact, Christianity at this moment in time was seen as a sect within Judaism. However, it was not going to be the same story once the disciples decided to cross the ethnic boundary in order to go to the ends of the world. 
How were they to make this new “religion” appealing to a people who had been considered “outsiders” and unworthy of religion? How were they to make Christianity inclusive (as opposed to the exclusivity of its parent religion, Judaism) without compromising its values? As the disciples were soon finding out, this wasn’t going to an easy thing to accomplish. Selling Christianity to the Gentiles wasn’t going to be easy. But I believe they were more surprised to realize that the first hurdle they had to overcome was from within. Some conservative members of the Christian community (circumcised believers) were apparently not happy with the step Peter took of entering the house of a gentile, uncircumcised believer. In his defense, Peter reminds them that he too had shared in their belief and had himself taken such a stance until he was “converted” through a vision.
In the vision, Peter is reminded that continuing to hold on to his conservative view was not only a retrogression but also a nullification of what God had accomplished in Jesus Christ. For in Jesus Christ, God had broken the walls of division and gathered the human race into one family of God. In Jesus Christ, there was no longer a Jew or gentile, a slave or free person (cf. Galatians 3:28). Although the Jews were the first to be called, Jesus’ mission had been extended to all (cf. John 10:16) for Jesus had offered himself for the salvation of all. After all, this was the very message that the disciples were charged with disseminating to the ends of the earth: that in Jesus Christ, God has reconciled the universe to God-self. In Jesus Christ, God has re-created the universe and has made it new (clean). In Jesus Christ, even those who were thought of as unclean and unworthy of God were now clean and worthy recipients of God’s salvation.