Blessed - Happy are they: they are highly favored; see the note at Matthew 5:3.
Whose sins are covered - Are concealed; or hidden from the view. On which God will no more look, and which he will no more remember. "By these words," says Calvin (in loco), "we are taught that justification with Paul is nothing else but pardon of sin." The word "cover" here has no reference to the atonement, but is expressive of hiding, or concealing that is, of forgiving sin.

Blessed are they whose iniquities are forgiven - That is, the man is truly happy whose iniquities αι ανομιαι, whose transgressions of the law are forgiven; for by these he was exposed to the most grievous punishment. Whose sins, αι αμαρτιαι, his innumerable deviations from the strict rule of truth and righteousness, are covered - entirely removed out of sight, and thrown into oblivion. See the meaning of the word sin in the note on Genesis 13:13 (note).

Saying, blessed are they,.... These words are cited from Psalm 32:1, and contain the proof of the happiness of justified persons. In this citation the singular number is changed into the plural, to take in all sorts of men, Jews and Gentiles, and very agreeably to the sense of the original; for the word may be rendered "blessed are they", or, "O the blessednesses"; that is, of everyone of them,
whose iniquities are forgiven, and whose sins are covered: such whom God justifies by imputing the righteousness of his Son to them, he removes their iniquities from them, which is meant by their being "forgiven", and that "as far as the east is from the west", Psalm 103:12; he casts them behind his back, Isaiah 38:17, and into the depths of the sea, Micah 7:19, so that they shall never be found more: such whom he clothes with the robe of righteousness, and garments of salvation, Isaiah 61:10, "their sins are covered"; from the eye of divine justice, and shall never be seen more, or be brought against them to their condemnation, and therefore must be happy persons. The (e) Jews tell us, that
"on the day of atonement Satan comes to accuse Israel, and he particularizes their sins, and the holy blessed God he particularizes their good works, and takes a pair of balances, and puts their sins against their good works, and weighs the one against the other; and when the two scales of the balances are alike, Satan goes to bring in other sins to overweigh; what does the holy blessed God do? he takes the sins out of the scale, and hides them , "under his purple garment"; and when Satan comes and finds no iniquity there, as it is said "the iniquity of Israel shall be sought for, and there shall be none", Jeremiah 50:20; and when Satan sees this, he says before him, Lord of the world, "thou hast taken away the iniquity of thy people, thou hast covered all their sin", Psalm 85:2. Selah.''
The purple garment they explain by , "his garment of mercy"; which is true of the mercy of God covering the sins of his people, through the purple blood of his Son; which is the purple covering of Christ, Song 3:10, under which the saints go safe to glory, and by which blood their crimson and scarlet sins are blotted out, so as never to be seen more.
(e) Caphtor, fol. 59. 1, 2.

Saying, Blessed, &c.-- (Psalm 32:1-2). David here sings in express terms only of "transgression forgiven, sin covered, iniquity not imputed"; but as the negative blessing necessarily includes the positive, the passage is strictly in point.

Happy are they whose sins are covered - With the veil of divine mercy. If there be indeed such a thing as happiness on earth, it is the portion of that man whose iniquities are forgiven, and who enjoys the manifestation of that pardon. Well may he endure all the afflictions of life with cheerfulness, and look upon death with comfort. O let us not contend against it, but earnestly pray that this happiness may be ours! Psalm 32:1-2.