For I will be merciful to their unrighteousness
That is, sin; for all unrighteousness is sin, being contrary to
the justice of God, and his righteous law: and the phrase is
expressive of God's forgiveness of it, which is a very
considerable article of the covenant of grace; mercy is the
spring and original of pardon; it is what God delights in, and
therefore he pardons freely; it is large and abundant, and hence
he pardons fully; and this lays a foundation for hope in sensible
sinners: and the way and means, in and by which God pardons, is
the propitiatory sacrifice of his Son; and the word here rendered
"merciful", signifies "propitious"; God pardons none but those to
whom he is pacified, or rendered propitious by Christ; there is
no mercy, nor pardon, but through him; he pardons on the foot of
reconciliation and satisfaction for sin by Christ; so that
forgiveness of sin is an act of justice, as well as of mercy; or
it is an act of mercy streaming through the blood and sacrifice
of Christ.
And their sins and their iniquities will I remember no
more;
by which are meant all kind of sin, original and actual; sins
before and after conversion; every sin but that against the Holy
Ghost, and that God's covenant people are never guilty of; these
God remembers no more; he casts them behind his back, and into
the depths of the sea, so that when they are sought for, they
shall not be found; God will never charge them with them, or
punish them for them: this is another phrase to express the
forgiveness of sins, and distinguishes the new covenant from the
old one, or the former dispensation; in which, though there were
many typical sacrifices, and a typical removal of sin, yet there
was a remembrance of it every year.