So let no one separate the Old Testament from the New Testament; let no one say that there there was one Spirit and here another: he would offend the Holy Spirit, who is honoured with the Father and with the Son and is numbered in the Holy Trinity at the moment of baptism. The only-begotten Son of God says explicitly to the apostles: "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit" (Mt 28:19). Our hope is placed in the Father, in the Son and in the Holy Spirit. We do not proclaim three gods; the Marcionites are dumbstruck because with the Holy Spirit we proclaim one God, through one Son. Faith is indivisible, piety inseparable. We do not divide the Trinity, as some do, and we do not create confusion like Sabellius; instead we know very well that the one Father sent his Son to us as the Saviour; we know that the only-begotten Son sent the promised Paraclete from the Father (cf. Jn 15:26). We know that the Holy Spirit spoke through the prophets, and came down on the Apostles at Pentecost in the form of tongues of fire (cf. Acts 1:1-3), here in Jerusalem, in the Upper Room of the Apostles. We have all the privileges: here Christ came down from heaven and here also the Holy Spirit came down from heaven. In truth it would be much more fitting that, just as we spoke of Christ and Golgotha at Golgotha, so we would speak of the Holy Spirit in the Upper Room. Since he who came down there shares the same glory as he who was crucified, we speak here of the One who came down there: in fact, piety is indivisible. (Cyril of Jerusalem)