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 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.