From the Letters of St. Jerome, CXXXIII:
It is in vain that you misrepresent me and try to convince the ignorant that I condemn free-will. Let him who condemns it be himself condemned. We have been created endowed with free-will; still it is not this which distinguishes us from the brutes. For human free-will, as I said, depends upon the help of God and needs His aid moment by moment, a thing which you and yours do not choose to admit. Your position is that once a man has free-will he no longer needs the help of God. It is true that freedom of the will brings with it freedom of decision. Still man does not act immediately on his free-will but requires God’s aid who Himself needs no aid.