There are three ranks of those who are being saved. The first kind are like slaves who do what is good because they fear the judgment. This is what David means when he says, Nail down my flesh with the fear of Thee, for of Thy judgments am I afraid. [Ps. 118:120]

The second kind, who are like hired servants, are those who are eager to serve God because of their desire for the reward of good things, as David again says, I have inclined my heart to perform Thy statutes for ever for a recompense. [Ps. 118:112]

But if they are of the third kind, that is, if they are sons, they keep His commandments out of love for God. This is what David means when he says, O how I have loved Thy law, O Lord! The whole day long it is my meditation; [Ps. 118:97] and again, with no mention of fear, I lifted up my hands to Thy commandments which I have loved, [Ps. 118:48] and again, Wonderful are Thy testimonies, and because they are wonderful, therefore hath my soul searched them out. [Ps. 118:129]