We proceed to the second article thus:
1. It seems that no preparation or disposition for grace is required on the part of man. For the apostle says (Rom.4:4): "Now to him that worketh  is the reward not reckoned of grace, but of debt." But a man could not of his own free will prepare himself for grace, unless by an operation. The meaning of grace would then be taken away.
2. Again, a man who walks in sin does not prepare himself for grace. Yet grace is given to some while they walk in sin. This is evident in the case of Paul, who received grace while "breathing out threatenings and slaughter against the disciples of the Lord" (Acts.9:1). Hence no preparation for grace is required on the part of man.
3. Again, an agent whose power is infinite does not need any disposition of matter, since he does not even need matter itself, as is obvious in creation. Now grace is likened to creation, being called a new creature in Gal., ch.6, and it was said in the preceding article that God, whose power is infinite, is the sole cause of grace. It follows that no preparation for receiving grace is required on the part of man.
On the other hand: it is said in Amos 4:12: "prepare to meet thy God, O Israel," and in I Sam.7:3: "prepare your hearts unto the Lord."
I answer: as we said in Q.111, Art.2, grace may be understood in two ways. Sometimes it means a habitual gift which God bestows. At other times it means the help of God, who moves the soul to good. Now some preparation is required for grace as a habitual gift, since a form can exist only in matter which is disposed to it. But no previous preparation is required on the part of man if we are speaking of grace as the help of God, by which he moves him to good. Rather is any preparation which can take place within him due to the help of God, who thus moves him. Even the good action of his free will, by which he is made ready to receive the gift of grace, is an action of his free will as moved by God. Hence a man is said to prepare himself. As it is said in Prov.16:1: "the preparations of the heart in man."  But since his free will is moved by God as principal agent, his will is also said to be prepared by God, and his steps guided by the Lord.
On the first point: there is a preparation of oneself for grace which is simultaneous with the infusion of grace. This is indeed a meritorious work. But it merits the glory which a man does not yet possess, not the grace which he now has. There is also an incomplete preparation for grace which sometimes precedes sanctifying grace, though nevertheless due to God as mover. But this last is not sufficient for merit, since there is as yet no justification by grace. As we shall show in Q.114, Art.2, there is no merit except by grace.
On the second point: since a man cannot prepare himself for grace unless God first moves him to good, it is immaterial whether one is perfectly prepared all at once, or little by little. As it is said in Ecclesiasticus 11:21: "In the eyes of God, it is easy for a poor man suddenly to become rich." Sometimes God moves a man to good, but not perfectly. This is a preparation which precedes grace. At other times he moves a man to good both instantaneously and perfectly, and such a one then receives grace suddenly, after the manner spoken of in John 6:45: "Every man therefore that hath heard, and hath learned of the Father, cometh unto me." This is what happened to Paul, whose heart was suddenly moved by God to hear, to learn, and to come, even while he yet walked in sin. He thus received grace suddenly.
On the third point: an agent whose power is infinite needs neither matter nor a disposition of matter provided by the action of any other cause. Such an agent is nevertheless bound to cause both the matter in a thing and a disposition favourable to its form, according to the condition of the thing to be made. So likewise when God infuses grace into the soul, no preparation is required which God does not himself achieve.
 qui operatur.  Migne: "It is of man to prepare the soul."
 Migne: "It is of man to prepare the soul."