Faith is a grace
When St. Peter confessed that Jesus is the Christ, the Son of the living God, Jesus declared to him that this revelation did not come "from flesh and blood", but from "my Father who is in heaven". Faith is a gift of God, a supernatural virtue infused by him. "Before this faith can be exercised, man must have the grace of God to move and assist him; he must have the interior helps of the Holy Spirit, who moves the heart and converts it to God, who opens the eyes of the mind and 'makes it easy for all to accept and believe the truth.'"
Source: Catechism of the Catholic Church (Vatican.va)