The Cost of Public Christianity

Contrast [the] modern casualness with the early church’s deep theology surrounding conversion and especially the costly stress on the public witness of the sacrament of baptism.  This was a direct and deliberate counterpoint to the Roman practice of sacrament.  For the Romans, the sacramentum was far more serious than a normal oath in law court.  It was a solemn vow by which a person gave his or her word before an authority and put his or her life in forfeit as a guarantee of what had been sworn.  Those who had given their sacramentum were then sacer. They were “given to the gods” if they violated their vow. They had given their sacred bond and they were no longer their own. …

For Christians, then, baptism was no casual choice. It was a public vow, a decisive break with the past and a solemn binding oath of allegiance to Jesus, sworn to God and before God—and before their fellow believers and the watching world. This was probably one reason why there were so many deathbed baptisms, such as the Emperor Constantine’s (“I am now numbered among the people of God. . . .  I shall now set out for myself rules of life which befit God”).  People did not wish to die unforgiven, but neither did they wish to commit themselves any earlier than they needed to live under a vow (sacramentum) that was so costly and so binding.  Choice today can always be casual, whereas the covenantal vow of faith is costly because we commit ourselves to Jesus and mortgage our very selves as we do so.  We have chosen, and we are committed.  We have picked up our crosses, and there is no turning back. We are no longer our own.

Os Guinness, Impossible People, pg.70-71