Why had Peter never eaten common or unclean food before meeting Cornelius?
Peter had never eaten anything common or unclean because he was still a law-keeping Jew. His adherence to the Law kept him from such foods, and that dietary separation reflected the broader barrier between Jew and Gentile that God was about to address through Cornelius.
Les explains that Peter said he had never eaten anything that was common or unclean because he was still a law-keeping Jew. When Peter arrived at the threshold of Cornelius’s house, he was almost shaking in his boots, but knowing that God was forcing the issue, he went in. Peter also said it was an unlawful thing for him, a Jew, to keep company with someone of another nation. After Cornelius rehearsed all that had happened to him, Peter became confident that God was evidently going to deal with this Gentile. Even though Peter had a hard time comprehending it, he had to recognize that God was doing something totally different.