Was reading Hugh Martin on the atonement and he has a fairly lengthy discussion on Christ as a priest in his sacrifice of himself. We quite easily say that he was both the offerer and the offering, but to stop and think about the apparent contradiction of that is mind bending. One thing it does is highlight the intentionality of Christ in the atonement. He was by no means a victim, martyr, mere example, or universal scapgoat…He was a priest in his offering. He was making an offering to the Father, with God as the focus. Perhaps a good question for anyone who denies penal substitution is to ask in what way Christ was acting as a priest in his death.
Many times the death of Christ is, perhaps regretfully, described as his passive obedience (in contrast with his life, his active obedience, and I understand the intention in making this disctinction), but in thinking about Christ as priest in his sacrifice, he was anything but passive. He was being offered, and was offering. Not sure how that works, but that is the testimony of scripture.