The Holy Spirit was able to speak to Peter about the salvation of Cornelius and all Gentiles because Peter had made himself fully available to the work of God. Though Peter didn’t understand everything up front, he'd given himself fully to Jesus and obeyed the Holy Spirit. The result? The Gentile Pentecost. You and I are not Jews today because Peter obeyed God and went to Cornelius.
You may be a Christian–your sins are forgiven, and you live a holy life. But have you devoted your life to the work of the gospel? Is everything on the line for revival? Are you willing to do the same thing Peter did? If not, how will you be able to stand in the Day of Judgment?