Wolfgang Musculus on Ephesians 4:5
Baptism is initiation and consecration in the name of the Father, the Son and the Holy Spirit, and it is incorporation into the church and the communion of saints. This is why there is not one baptism for one person and another for another, but all are baptized in the same way. Therefore, since we are all set apart by one and the same baptism and not by different ones, we are reminded that the harmony and unanimity of the church is maintained by the oneness of this sacrament …
It may however be asked how baptism can be one when Christ and the apostles, and later others who were baptized by the apostles at Christ’s command, were baptized with John’s baptism, if John’s baptism and Christ’s are not the same. Furthermore, how can baptism be one when it has three elements to it, water, fire and blood? Likewise, how can even the baptism of water alone, which the churches have practiced since the time of the apostles, be one, when some people give the Eucharist to newly baptized infants while others withhold it from them, when some baptize adults only, and others also baptize infants, when some immerse three times and others only once, when some immerse and others sprinkle, when some strip the baby naked and others uncover only its head, when some baptize with exorcisms, wax, salt, oil and spit, while others dispense with all that and use only water? Given such variety, how can we say that there is only one baptism in the church?
My answer is that the unity of baptism is not located in the circumstances of the ministers baptizing nor of those being baptized, or in rites and external ceremonies, but in the substance, that is to say, in the name of him into whom we are baptized, the one God who is Father, Son and Holy Spirit.