To continue j’s controversial thoughts on Jesus becoming sin for us,
here is some Barth on Jesus baptism
When He had Himself baptised with water by John, Jesus confessed both God and [humankind]. A better way of putting it is that because He confessed God, the God whose will was soon to be done on earth as it is in heaven, therefore He confessed [humankind], the [humans] who are in view in this doing of God’s will. Because He is committed unreservedly to subordination to God, therefore He is committed unreservedly to solidarity with [humankind]. He who as God’s Son was very different from all [people], being one with the Father who sent Him, and therefore Himself God, negated this difference, this distance, this strangeness between Himself and others, even to the last remnant. He became wholly and utterly one of them, not in an act of secret or even public condescension, like a king for a change donning a beggar’s rags and mingling with the crowd, but by belonging to them in every way, by being no more and no less than one of them, by having no point of reference except to them. He became one of them, not in order to renounce full fellowship with them when the game was over, like the king exchanging again the beggar’s rags for his kingly robes, not in order to leave again the table where He had seated Himself with publicans and sinners , and to find himself a better place, but in order to be one of them definitively as well as originally, unashamed to call them brethren to all eternity because He was their Brother from all eternity (Heb. 2:11), a veritable King in this true form of His, and at His place of honour. With the men of His people, then, He received the Word of God which came to John and to which John bore witness. With them He looked forward to the intimated new act of God which would change all things. With them He looked forward to the establishment of God’s kingdom, the threatened judgment, the remission and taking away of their sins. With them He obeyed the call for conversion issued to his people. With all the rest He had Himself baptised with water. With them He thus confessed His sins. His sins? If we do not say this, we question and even deny the totality of His self-giving to [humankind], and therewith the totality of His self-giving to God. We say that He had Himself baptised with the rest only improperly, contrary to the meaning of John’s preaching and baptism, in a demonstration which had neither truth nor necessity for Him. We say at root that this was just a theatrical show. But it was not a theatrical show. The seriousness with which others, frightened before God and setting their hope in Him alone, confessed their sins, is infinitely surpassed hereby the divine earnestness with which this One, when faced by the sins of all others, their confusions and corruptions, their big and little acts of ungodliness, did not let these sins be theirs, did not regard, bewail or judge them from a distance with tacit or open accusation, did not simply characterise them as sins by His own Otherness, but as the Son of His Father, elected and ordained from all eternity to be the Brother of these fatal brethren, caused them to be His own sins, confessed them as such, and therewith confessed that He was baptised in prospect of God’s kingdom, judgment and forgiveness. No one who came to the Jordan was as laden and afflicted as He. No one was as needy. No one was so utterly human, because so wholly fellow-human. No one confessed his sins so sincerely, so truly as his own, without side-glances at others. He stands alone in this, He who was elected and ordained from all eternity to partake of the sin of all in His own person, to bear its shame and curse in the place of all, to be the man responsible for all, and as such, wholly theirs, to live and act and suffer. This is what Jesus began to do when He had Himself baptised by John with all the others. This was the opening of His history as the salvation history of all the others.
~Karl Barth, CD IV/4, 58-59.
Ht Halden at inhabitatio Dei