Summa contra Gentiles3.161 Chapter CLXI. That God delivers some from sin, and leaves some in sin

Now, though he that sins places an obstacle to grace, and so far as the order of things demands, ought not to receive grace: yet, since God can act independently of the order implanted in things, as when He enlightens the blind, or raises the dead, sometimes of the richness of his bounty, He comes to the assistance of those who put an obstacle in the way of grace, turns them from evil, and converts them to good. And even as He enlightens not all the blind, nor heals all the sick, in order that in those whom He restores the work of His power may be evidenced, and in the others, the order of nature be maintained; so too, He comes not to the assistance of all who hinder grace, that they may turn away from evil, and be converted to good; but of some, in whom He wishes His mercy to appear; while in the others the order of justice is made manifest. Hence the Apostle says (Rom. ix. 22): God willing to show His wrath, and to make His power known, endured with much patience vessels of wrath, fitted for destruction, that he might show the riches of His glory on the vessels of mercy, which He hath prepared unto glory. And if of those who are held in thrall by sins God converts some by His prevenient grace, while others He suffers or allows, in the ordinary way, to continue sinning, we are not to ask why He converts certain ones and not others. For this depends on His simple will: even as it came from His simple will, that whereas all things were made out of nothing, some were made to rank higher than others: and just as it depends on the simple will of the craftsman that of the same matter similarly conditioned. He make some vessels for dignified purposes, and some for common purposes. Hence the apostle says (Rom. ix. 21): Hath not the potter power over the clay, of the same lump to make one vessel unto honour, and another unto dishonour?

Hereby we refute the error of Origen who said that these are converted to God and not those, on account of certain works done by their souls before they were united to bodies. In the Second Book, we gave more particular attention to the refutation of this opinion.