"Christ declares that the doctrine of the Gospel, though it is preached to all without exception, cannot be embraced by all, but that a new understanding and a new perception are requisite; and, therefore, that faith does not depend on the will of men, but that it is God who gives it."
"… faith is not bare or cold knowledge, since no man can believe who has not been renewed by the Spirit of God … faith itself is a work of the Holy Spirit, who dwells in none but the children of God. So then, in various respects, faith is a part of our regeneration, and an entrance into the kingdom of God, that he may reckon us among his children. The illumination of our minds by the Holy Spirit belongs to our renewal, and thus faith flows from regeneration as from its source; but since it is by the same faith that we receive Christ, who sanctifies us by his Spirit, on that account it is said to be the beginning of our adoption."
Source: John Calvin, Commentary on John