Augustine of Hippo

Those and other divine testimonies, which it would take too long to enumerate, show that God by his grace takes away the stony heart from unbelievers and forestalls merit in people of good will in such a way that their will is prepared by prevenient grace, but not that grace is given through prevenient merit of the will. This is shown both by thanksgiving and by prayer: prayer for unbelievers; thanksgiving for believers. Prayer is to be made to him that he may do what we ask; thanksgiving is to be offered when he has done it.

Letter 217 ↗