The American Calvinist theologian John Murray (one of the founders of Westminster Theological Seminary) discussing regeneration and faith in his book Redemption: Accomplished and Applied (pg. 106):

Regeneration is the act of God and of God alone. But faith is not the act of God; it is not God who believes in Christ for salvation, it is the sinner. It is by God’s grace that a person is able to believe but faith is an activity on the part of the person and of him alone. In faith we receive and rest upon Christ alone for salvation.

It might be said: this is a strange mixture. God alone regenerates. We alone believe. And we believe in Christ alone for salvation. But this is precisely the way it is. It is well for us to appreciate all that is implied in the combination, for it is God’s way of salvation and it expresses his supreme wisdom and grace. In salvation God does not deal with us as machines; he deals with us as persons and therefore salvation brings the whole range of our activity within its scope. By grace we are saved through faith (cf. Eph. 2:8).

John Murray