A Nazirite (******) was an Israelite who had taken special vows of dedication to Yahweh whereby he abstained for a specified period of time from using alcohol and grape products, cutting his hair, and approaching corpses. At the end of the period he was required to immerse himself in water. Thus the baptism of Jesus (Matthew 3:13-15) by John the Baptist could have been done ``to fulfil all righteousness'' at the ending of a nazirite vow. Following his baptism, the gospels give no reason to suppose Jesus took another nazirite vow until The Last Supper, (see Mark 14:25).
John the Baptist
Jesus