Again a voice [came] to him a second time, “What God has cleansed, no [longer] consider unholy.”
Peter’s vision came to him before Cornelius — the centurion to whom he was about to go — had received the Holy Spirit of been baptized or done much of anything except place his trust in God. Cornelius was saved, but that is about as far as things had gotten. Yet God declares Cornelius holy. While Peter’s vision has been variously interpreted, I think that the context of the vision — just before the messengers from Cornelius arrived to take Peter down to visit with a Gentile — supports the idea that the one whom God declares holy is holy and whom God declares clean is clean. Plain and simple.
I have noticed that there are times when I do not feel holy. I look at my life and at how messed up I still am and how much more work God has in store for Himself if He ever wants to fit me for Heaven and I mentally sigh and declare myself unholy. How I feel and whether or not a seemingly endless backlog of work remains for God to complete before I am fit for Heaven is not relevant. If God has declared me holy, then I am holy. No ifs, ands, or buts.
My right standing with God does not depend on me, but on what Christ did for me on the cross. My holiness; my set-apart-ness for God’s use is not mine to determine, but God’s. It is He Who is at work in me both to will and to do of His good pleasure.