It was necessary, then, for the copies of the heavenly things to be purified with these sacrifices, but the heavenly things themselves with better sacrifices than these. 24For Christ did not enter a sanctuary made with human hands that was only a copy of the true one; he entered heaven itself, now to appear for us in God’s presence. 25Nor did he enter heaven to offer himself again and again, the way the high priest enters the Most Holy Place every year with blood that is not his own. 26Otherwise Christ would have had to suffer many times since the creation of the world. But he has appeared once for all at the culmination of the ages to do away with sin by the sacrifice of himself. 27Just as people are destined to die once, and after that to face judgment, 28so Christ was sacrificed once to take away the sins of many; and he will appear a second time, not to bear sin, but to bring salvation to those who are waiting for him. Heb 9:23-28 NIV
This thread has touched on other concepts such as Grotius' Governmental Theory:
but this theory falls foul of verses that talk about Christ bearing our sins (although the difference is subtle rather than obvious to me at least).
He himself bore our sins” in his body on the cross, so that we might die to sins and live for righteousness; “by his wounds you have been healed.” 1 Pet 2:24 NIV
There is a green hill far away,
outside a city wall,
where our dear Lord was crucified
who died to save us all.
We may not know, we cannot tell,
what pains he had to bear,
but we believe it was for us
he hung and suffered there.
He died that we might be forgiven,
he died to make us good,
that we might go at last to heaven,
saved by his precious blood.
There was no other good enough
to pay the price of sin,
he only could unlock the gate
of heaven and let us in.
O dearly, dearly has he loved!
And we must love him too,
and trust in his redeeming blood,
and try his works to do.
sung by King's College Choir: