Ps 102:18

“"And His righteousness upon children's children" (ver. 18). He speaketh of reward, "upon children's children." How many servants of God are there who have not children, how much less children's children? But He calleth our works our children; the reward of works, our "children's children." "Even upon such as keep His covenant." Let men beware that all may not conceive what is here said to belong to themselves: let them choose, while they have the choice. "And keep in memory His commandments to do them." Thou wast already disposed to flatter thyself, and perhaps to recite to me the Psalter, which I have not by heart, or from memory to say over the whole Law. Clearly thou art better in point of memory than I, better than any righteous man who doth not know the Law word for word: but see that thou keep the commandments. But how shouldest thou keep them? Not by memory, but by life. "Such as keep in memory His commandments:" not, to recite them; but, "to do them." And now perhaps each man's soul is disturbed. Who remembereth all the commandments of God? who remembereth all the writings of God? Lo, I wish not only to hold them in my memory, but also to do them in my works: but who remembereth them all? Fear not: He burdeneth thee not: "on two commandments hang all the Law and the Prophets." ...”

“For then only may His words be said to abide in us, when we do what He has commanded us, and love what He has promised. But when His words abide only in the memory, and have no place in the life, the branch is not to be accounted as in the vine, because it draws not its life from the root. It is to this distinction that the word of Scripture has respect, "and to those that remember His commandments to do them." For many retain them in their memory only to treat them with contempt, or even to mock at and assail them. It is not in such as have only some kind of contact, but no connection, that the words of Christ abide; and to them, therefore, they will not be a blessing, but a testimony against them; and because they are present in them without abiding in them, they are held fast by them for the very purpose of being judged according to them at last.”