“Prayer relies on mercy,” says St. Thomas, “condign merit on justice. And therefore man obtains from the divine mercy many things by prayer which he does not merit in strict justice.”(1349) This teaching is based partly on Holy Scripture and partly on the writings of St. Augustine, and is confirmed by certain utterances of the Council of Trent. By conscientiously preparing himself with the aid of actual grace, the sinner probably merits an additional claim (in equity) to justification. Cfr. Ps. L, 19: “A sacrifice to God is an afflicted spirit: a contrite and humbled heart, O God, thou wilt not despise.”(1350) Dan. IV, 24: “Redeem thou thy sins with alms, and thy iniquities with works of mercy to the poor: perhaps he [God] will forgive thy offences.”(1351) St. Augustine says: “The remission of sins itself is not without some merit, if faith asks for it. Nor is that faith entirely unmeritorious by which the publican was moved to say: ‘God, be merciful to me, a sinner,’ and then went away justified through the merit of faithful humility.”(1352) b) By good works the just may merit for themselves, not in strict justice (_de condigno_), but as a matter of equity (_de congruo_), final perseverance, conversion from mortal sin, spiritual favors for others, and also such temporal blessings as may be conducive to eternal salvation. α) It is a theologically certain conclusion, accepted by all theologians without exception, that the grace of final perseverance (_donum perseverantiae_) cannot be merited in the strict sense (_de condigno_). Most authors hold, however, that it can be merited de congruo. This _meritum_ is technically called _meritum de congruo fallibili_. Those who deny that it can be merited at all, admit that it can be infallibly obtained by fervent and unremitting prayer.(1353)