Irresistible Grace is a Reformed teaching that states that when God calls His elect into salvation that they cannot resist. God offers to all people the gospel message. This is called the external call. But to the elect God extends an internal call, and it cannot be resisted. This call is by the Holy Spirit who works in the hearts and minds of the elect to bring them to repentance and regeneration whereby they willingly and freely come to God.
Some of the verses used in support of this teaching are: Romans 9:16 where it says that "it is not of him who wills nor of him who runs, but of God who has mercy," Philippians 2:12-13 where God is said to be the one working salvation in the individual, John 6:28-29 where faith is declared to be the work of God, Acts 13:48 where God appoints people to believe, and John 1:12-13 where being born again is said to be not by man’s will but by God’s.