Righteousness for the Unrighteous

“He that believeth is not condemned” (John 3:18). This is the negative side;
and even were there no more for us, this would be blessedness, seeing our
portion was by nature that of “children of wrath.” But there is more; for it
is written, “All that believe are justified from all things” (Acts 13:39);
and “Christ is the end (or fulfilling) of the law for RIGHTEOUSNESS to every
one that believeth” (Rom 10:4). “As by the offense of one, judgment came upon
all men to condemnation; even so by THE RIGHTEOUSNESS OF ONE, the free gift
came upon all men unto JUSTIFICATION OF LIFE” (Rom 5:18).

The strength or kind of faith required is nowhere stated. The Holy Spirit has
said nothing as to quantity or quality, on which so many dwell, and over which
they stumble, remaining all their days in darkness and uncertainty. It is simply
in believing,-feeble as our faith may be,-that we are invested with this
righteousness. For faith is no work, nor merit, nor effort; but the cessation
from all these, and the acceptance in place of them of what another has done,
-done completely, and for ever. The simplest, feeblest faith suffices; for it
is not the excellence of our act of faith that does aught for us, but the
excellence of Him who suffered for sin, the just for the unjust, that He might
bring us to God. His perfection suffices to cover not only that which is
imperfect in our characters and lives, but that which is imperfect in our
faith, when we believe on His name.

Horatius Bonar, The Everlasting Righteousness