Romans 3:25,26

The death of Christ had a twofold object or final cause: — (1) It was to be, like the sacrifices of the old covenant, an offering propitiatory to God, and actualised in the believer through faith. (2) It was to demonstrate the righteousness of God by showing that sin would entail punishment, though it might not be punished in the person of the sinner. The apparent absence of any adequate retribution for the sins of past ages made it necessary that by one conspicuous instance it should be shown that this was in no sense due to an ignoring of the true nature of sin. The retributive justice of God was all the time unimpaired. The death of Christ served for its vindication, at the same time that a way to escape from its consequences was opened out through the justification of the believer.
Precisely in what sense the punishment of our sins fell upon Christ, and in what sense the justice of God was vindicated by its so falling, is another point which we are not able to determine. Nothing, we may be sure, can be involved which is in ultimate conflict with morality. At the same time, we see that under the ordinary government of God, the innocent suffer for the guilty, and there may be some sort of transference of this analogy into the transcendental sphere. Both the natural and the supernatural government of God are schemes “imperfectly comprehended.” In any case, Christ was innocent, and Christ suffered. On any theory there is a connection between His death and human sin. What connection, is a question to which, perhaps, only a partial answer can be given. Some weighty remarks on this subject will be found in Butler’s Analogy of Religion, Part II., Romans 5 (latter part).