I have blotted out, as a thick cloud, thy transgressions, and, as a cloud, thy sins: return unto me; for I have redeemed thee.
I have blotted out - the debt of thy sin from the account-book in which it was entered (Exodus 32:32-33; Revelation 20:12). How blessed to have our sin "blotted out" - our names never 'blotted out of the book of life?' (Revelation 3:5.)
As a thick cloud, thy transgressions - scattered away by the wind, "as far as the east is from the west" (Psalms 103:12).
As a cloud, thy sins - a descending gradation. Not only the "thick cloud" of the heavier "transgressions," but the "cloud" ('vapour,' Lowth; not so dense, but covering the sky as a mist) of the countless "sins." These latter, though not thought much of by man, need, as much as the former, to be cleared away by the Sun of righteousness, else they will be a mist separating us from heaven (Psalms 19:12-13; 1 John 1:7-9).
Return unto me, for I have redeemed thee. The antecedent redemption is the ground of, and motive to, repentance. We do not repent in order that He may redeem us, but because He hath redeemed us (Zechariah 12:10; Luke 24:47; Acts 3:18-19). He who believes in his being forgiven cannot but love, like the forgiven woman who washed her Saviour's feet with her tears, and wiped them with the hair of her head, and anointed Him in Simon the Pharisee's house (Luke 7:43; Luke 7:47).