All four canonical Gospels describe John the Baptist, an ascetic preacher active in the Judean wilderness, baptizing people in the Jordan River as a sign of repentance, and all four connect Jesus to this ministry through his own baptism by John. Mark, generally regarded by scholars as the earliest of the four Gospels to be written, gives the most compact account: Jesus comes from Nazareth, is baptized by John, and as he comes up out of the water sees the heavens torn open, the Spirit descending like a dove, and hears a voice declaring him God's beloved son.
Matthew and Luke both preserve the same core scene while adding further detail; Matthew includes an exchange in which John initially objects to baptizing Jesus, protesting that Jesus should baptize him instead, a hesitation many scholars read as reflecting later Christian discomfort with the theological implications of Jesus receiving baptism from John rather than the reverse. John's Gospel, by contrast, does not narrate the baptism directly as an event but has John the Baptist testify afterward to having seen the Spirit descend on Jesus.
The episode marks the beginning of Jesus's public ministry across the Synoptic Gospels, and it introduces, within the space of a single scene, the Father's voice, the Son being baptized, and the Spirit descending, an association later Christian theology developed into one of the clearest scriptural anchors for the doctrine of the Trinity.