Ephesians 2:4

Here the apostle begins his account of the glorious change that was wrought in them by converting grace, where observe, I. By whom, and in what manner, it was brought about and effected. 1. Negatively: Not of yourselves, Eph 2:8. Our faith, our conversion, and our eternal salvation, are not the mere product of any natural abilities, nor of any merit of our own: Not of works, lest any man should boast, Eph 2:9. These things are not brought to pass by any thing done by us, and therefore all boasting is excluded; he who glories must not glory in himself, but in the Lord. There is no room for any man's boasting of his own abilities and power; or as though he had done any thing that might deserve such immense favours from God. 2. Positively: But God, who is rich in mercy, etc., Eph 2:4. God himself is the author of this great and happy change, and his great love is the spring and fontal cause of it; hence he resolved to show mercy. Love is his inclination to do us good considered simply as creatures; mercy respects us as apostate and as miserable creatures. Observe, God's eternal love or good-will towards his creatures is the fountain whence all his mercies vouch-safed to us proceed; and that love of God is great love, and that mercy of his is rich mercy, inexpressibly great and inexhaustibly rich.

— Matthew Henry's Concise Commentary (public domain)

God, who is rich--Greek "(as) being rich in mercy." for--that is, "because of His great love." This was the special ground of God's saving us; as "rich in mercy" (compare Eph 2:7; Eph 1:7; Rom 2:4; Rom 10:12) was the general ground. "Mercy takes away misery; love confers salvation" [BENGEL].

— Jamieson-Fausset-Brown Commentary (public domain)