I think what this question is really asking is whether or not God's
forgiveness must be conditioned upon the satisfaction of divine justice. The
shedding of blood there simply means that what justice demands is capital
punishment, that a capital crime has been committed and therefore the just desert
of the person who has committed this sin is death. And the question is, must divine
justice be satisfied in order for God to forgive? Well surprisingly Christian
theologians have differed on this question. A good number of the church
fathers thought that God could in fact forgive our sins without any
satisfaction of divine justice, but that God has chosen Christ's atoning death as
a means of satisfying his justice because there are certain goods, certain
benefits that will result from this. For example people will see the love of God
manifested in Christ's self-sacrificial death; they will see the holiness and the
justice of God manifested in the punishment that Christ endures for us.
So that God had good reasons for requiring the satisfaction of divine
justice and the imposition of a capital punishment for our sin, but it wasn't
necessary. On the other hand, the Protestant Reformers by and large argued
that since retributive justice is essential to the nature of God, that God
could not simply forgive without the satisfaction of divine justice. God is as
holy and just as he is loving and merciful, and so what God needed to do
was to find a way to express his love and mercy without compromising his
justice and holiness, and the Protestant Reformers said that
that is expressed in the substitutionary atonement of Christ as Christ, out of his
great love for us, takes upon himself the punishment that we deserve for our sin,
thereby satisfying divine justice and freeing up the grace of God to pardon
and redeem us.