This is the generation. I have just now observed, that by the demonstrative pronoun this, the Psalmist erases from the catalogue of the servants of God all counterfeit Israelites, who, trusting only to their circumcision and the sacrifices of beasts, have no concern about offering themselves to God; and yet, at the same time, they rashly thrust themselves into the church. Such persons may pretend to have delight in the service of God, by often coming to his temple, but they have no other design than to withdraw themselves from him as far as they can. Now, as nothing was more common in the mouths of each of them than to say, that they all belonged to the holy seed, the Psalmist has limited the name of holy generation to the true observers of the law; as if he had said, All who have sprung from Abraham, according to the flesh, are not, on that account, his legitimate children. It is, no doubt, truly said in many other places, as we shall see inPsalm 27, that those sought the face of God who, to testify their godliness, exercised themselves in the ceremonies before the ark of the covenant; that is to say, if they were brought thither by a pure and holy affection. But as hypocrites seek God externally in a certain way, as well as true saints, while yet they shun him by their windings and false pretences, David here declares that God is not sought in truth unless there go before a zealous cultivation of holiness and righteousness. To give the sentence greater emphasis, he repeats it, using the second person, and addressing his discourse to God. [1] It is as if he summoned before the judgment-seat of God hypocrites, who account it nothing falsely to use the name of God before the world; and he thus teaches us, that whatever they may say in their empty talk among men, the judgment of God will be a very different matter. He adds the word Jacob, for the confirmation of the same doctrine putting it for those who were descended from Jacob; as if he had said, Although circumcision distinguishes all the seed of Jacob according to the flesh from the Gentiles, yet we can only distinguish the chosen people by the fear and reverence of God, as Christ said, "Behold an Israelite indeed, in whom is no guile!" (John 1:47.)

Footnotes

1 - He first says, "That seek him," and next, "That seek thy face."

This is the generation of them that seek him - This describes the race of those who seek Him; or, this is their character. The word "generation" here is used evidently in the sense of "race, people, or persons." This is the character or description of the "persons" who seek His favor; or, this is the character of His true friends. The phrase "to seek God" is often used as descriptive of true piety: Psalm 9:10; Psalm 14:2; Psalm 63:1; Proverbs 8:17; Matthew 6:33; Matthew 7:7. It indicates an earnest desire to know Him and to obtain His favor. It denotes also humility of mind, and a sense of dependence on God.
That seek thy face, O Jacob - Margin, O "God of" Jacob. DeWette understands this as meaning that they would seek the face of God among His people; or that they who belonged to the race of Jacob, and who were sincere, thus sought the face of God. There is supposed to be, according to this interpretation, a distinction between the true and the false Israel; between those who professed to be the people of God and those who really were His people (compare Romans 9:6-8). It seems to me that the word is not used here as it is in the margin to denote the "God of Jacob," which would be a harsh and an unusual construction, but that it is in apposition with the preceding words, as denoting what constituted the true Jacob, or the true people of God. "This is the generation of them that seek him; this is the true Jacob, that seek thy face, O Lord." That is, this is the characteristic of all who properly belong to the race of Jacob, or who properly belong to God as his true people. The sense, however, is not materially affected if we adopt the reading in the margin.

This is the generation - This is the description of people who are such as God can approve of, and delight in.
That seek thy face, O Jacob - It is most certain that אלהי Elohey, O God, has been lost out of the Hebrew text in most MSS., but it is preserved in two of Kennicott's MSS., and also in the Syriac, Vulgate, Septuagint, Ethiopic, Arabic, and Anglo-Saxon. "Who seek thy face, O God of Jacob."
Selah - That is, It is confirmed; it is true. The persons who abstain from every appearance of evil, and seek the approbation of God, are those in whom God will delight.

This [is] the (b) generation of them that seek him, that seek thy face, O Jacob. Selah.
(b) Though circumcision separates the carnal seed of Jacob, from the Gentiles, yet he who seeks God, is the true Jacob and an Israelite.

This is the generation of them that seek him,.... The persons above described are such, who in every age are the generation of the children of God, and are accounted by him for a generation; they are such that seek him, in the first place, with their whole hearts, and in Christ, where they find him;
that seek thy face, O Jacob. By the "face" of God is meant the favour of God, the discoveries of his love, the light of his countenance, than which nothing is more desirable to gracious souls, or more sought after by them; and by Jacob is meant the God of Jacob; and so Apollinarius has it in his metaphrase; see Psalm 10:1; unless Christ should be intended, one of whose names is Israel, Isaiah 49:3; or the words may be supplied, as they are by some Jewish writers (m), "this is Jacob"; or the persons before described are the seed of Jacob, and who are called by his name: and it may be observed, that the church of God often bears the same name, Isaiah 43:1; and then the sense is, the persons whose characters are given above are fit to ascend, and stand in the holy hill of God, are Israelites indeed, in whom there is no guile.
Selah; on this word; see Gill on Psalm 3:2.
(m) Aben Ezra, Kimchi, & Ben Melech in loc.

Jacob--By "Jacob," we may understand God's people (compare Isaiah 43:22; Isaiah 44:2, &c.), corresponding to "the generation," as if he had said, "those who seek Thy face are Thy chosen people."

The generation - The true progeny which God regards. Face - His grace and favour, which is often called God's face.