The salvation won for us in Christ on the cross and in the resurrection(and giving of the Spirit and ascension, etc.) is not external to the person of Christ. Some, in their desire to safeguard the sovereignty of God and God's grace, make the salvation won in the cross a transaction external to the person of Jesus. To summarise the external transaction idea: there is a law and those who break it must die; you have broken the law (so have I), so you deserve to die.(So do I.) But Christ takes this punishment for us, satisfying the obligation of the law through his sacrifice on the cross. The price is paid to (well, here the theory runs into real trouble, with the answers varying from Satan to God the Father) and we are saved.
There are better ways to safeguard theologically the grace of God in the cross and our utter reliance on Christ's sacrifice than this. And there are lots of reasons why this crudity should be abandoned. One reason is because Christ is no longer the saviour in person. Salvation (no matter what metaphor you are using or prefer, whether it be sacrifice, redemption etc) is won in the very being of Jesus. This is the whole point of the hypostatic union: the union of human and divine in the person of Christ, fully lived out in his life, death and resurrection, saves us. He is my saviour in his person. (Adding another layer of meaning to the phrase 'Jesus is my personal saviour'. He saves me, and he saves me in his person, not outside it.) No external transaction due to an outside force that God must obey, but the union of human and divine, and the beginning of the hypostatic union of all creation in Christ.
