John Calvin Commentary Romans 6:3

"Or are ye ignorant that all we who were baptized into Christ Jesus were baptized into his death?" — Romans 6:3 (ASV)

Know ye not, etc. What he intimated in the last verse—that Christ destroys sin in his people—he proves here by mentioning the effect of baptism, by which we are initiated into his faith. For it is beyond any question that we put on Christ in baptism, and that we are baptized for this purpose—that we may be one with him.

But Paul takes up another principle—that we are then truly united to the body of Christ when his death brings forth its fruit in us. Indeed, he teaches us that this sharing in his death is what is to be mainly regarded in baptism, for not washing alone is set forth in it, but also the putting to death and the dying of the old man.

Therefore, it is evident that when we become partakers of the grace of Christ, the efficacy of his death immediately appears. But the benefit of this sharing in the death of Christ is described in what follows.