Why are the other persons of the Trinity—the Spirit and the Father—also mentioned at Jesus’ baptism?
The Spirit, descending like a dove on Jesus, enables him to do his work as Saviour. The dove is known as a sacrificial animal (for the poor people), and thus points to Jesus as the one who is going to sacrifice himself for sinful people. The Father speaks and makes it clear (by telling Jesus: You are my beloved Son
; a quote from Psalm 2:1–12) that he is very pleased about this baptism which shows that his only begotten Son is willing to die for sinful people.
10 Au moment où il sortait de l'eau, il vit les cieux s'ouvrir, et l'Esprit descendre sur lui comme une colombe.