Jesus was baptised with the baptism meant for sinners, the baptism of repentance, not for his own sake but for ours, and in him our humanity was anointed by the Spirit and consecrated in sonship to the Father. Thomas Torrance writes that,
For Jesus, baptism meant that he was consecrated as the Messiah, and that he, the Righteous One, became one with us, taking upon himself our unrighteousness, that his righteousness might become ours. For us, baptism means that we become one with him, sharing in his righteousness, and that we are sanctified in him as members of the messianic people of God, compacted together in one Body in Christ. There is one baptism and one Body through the one Spirit. Christ and his Church participate in the one baptism in different ways – Christ actively and vicariously as Redeemer, the Church passively and receptively as the redeemed Community.
So we can never speak of baptism as a sacrament of what we do, but only as what God has done for us in Christ, in whom he has bound himself to us and bound us to himself, before we could ever respond to him. But it is also the sacrament of what God does now in us by his Spirit, uniting us with Christ in his faithfulness and obedience to the Father and making that the ground of our faith. So as an act done to us, baptism tells us that it is not upon our own faithfulness that we rely, but upon Christ alone and his vicarious faithfulness; it also tells us that in the freedom of the Spirit, God makes himself present to us and secures us creatively to himself in such remarkable ways that not only is faith called from us as our own spontaneous response to God’s grace in Christ, but it is undergirded and sustained by Christ and enclosed with his own faithfulness, and so grounded in the mutual relation between the incarnate Son and the Father. For, as Calvin observed,
For he (i.e. Christ) dedicated and sanctified baptism in his own body [Matt. 3:13] in order that he might have it in common with us as the firmest bond of the union and fellowship which he has designed to form with us. Hence, Paul proves that we are children of God from the fact that we put on Christ in baptism [Gal. 3:26-27]. Thus we see that the fulfillment of baptism is in Christ, whom also for this reason we call the proper object of baptism. Consequently, it is not strange that the apostles are reported to have baptized in his name [Acts 8:16; 19:5], although they had also been bidden to baptize in the name of the Father and of the Spirit [Matt. 28:19]. For all the gifts of God proffered in baptism are found in Christ alone.
Thus, before we can even begin to speak of sacraments in general (or baptism in particular), or what Weber preferred to call ‘proclamation activities’, we must see how Jesus Christ himself, in his own Person, is the primary sacrament, as he is the primary mysterion and revelation of the Triune God. In this sense, we must also speak of revelation as sacrament. For God to reveal Godself, this revelation must be disclosed in creaturely objectivity, adapted to our creaturely existence and knowledge. The theological concept of sacrament is thus bound up in the structure and nature of God’s revelation.
Thus, there is ambiguity from the perspective of the human person – the objectification of divine revelation is not a prediction of the creaturely mind – and a provisional aspect to revelation – the final Word of revelation encompasses the ‘end of history as well as its significance. This is no less true of baptism where believers baptised in the name of the Triune God are thereby simultaneously set in the trinitarian history of God” so that there is an eschatological tension between the revelation of God in its historical form and in its ultimate reality. This is true both of revelation and sacrament as a sign of revelation. So Jesus Christ remains the mysterion through which all sacramental ‘mystery is mediated and objectively confirmed (1 Tim. 3:16). So Barth:
In the New Testament mysterion denotes an event in the world of time and space which is directly initiated and brought to pass by God alone, so that in distinction from all other events it is basically a mystery to human cognition in respect of its origin and possibility. If it discloses itself to man, this will be, not from without, but only from within, through itself, and therefore once again only through God’s revelation … Faith as a human action is nowhere called a mystery, nor is Christian obedience, nor love, nor hope, nor the existence and function of the ecclesia, nor its proclamation of the Gospel, nor its tradition as such, nor baptism, nor the Lord’s Supper. Would this omission have been possible if the New Testament community had been aware that certain human attitudes, actions and institutions were freighted with the divine word and act, if it had ascribed to baptism in particular the quality of a bearer and mediator of grace, salvation, and its manifestation?