All believers have one common vow which, made in baptism, we confirm and, so to speak, sanction by catechism and receiving the Lord’s Supper.  For the sacraments are like contracts by which the Lord gives us his mercy and from it eternal life; and we in turn promise him obedience.  But this is the form, or at least a summary, of the vow:  that, renouncing Satan, we yield ourselves to God’s service to obey his holy commandments but not to follow the wicked desires of our flesh.