Jesus fasts in, specifically, the wilderness, not because of a lack of food (see Matthew 3:4), but to be able to devote himself to God in prayer. Daniel shows how fasting was considered an aid to prayer (Daniel 9:3; Daniel 10:2–3,Daniel 10:12). Jesus is continuing his praying begun at his baptism (Luke 3:21), and is responding, as a Mediator, without being personally guilty, to John’s call: Repent, for the kingdom of heaven is at hand
(Matthew 3:2). He shares in his people’s weakness without being involved in their disobedience.
Jesus does not fast in the wilderness because of the lack of food available there (see Matthew 3:4), but because he wishes to completely devote himself to God in prayer without distraction. In Israel, fasting has always been considered an aid to prayer. It intensifies prayer and also provides it with the character of penance (see Daniel 9:3, Daniel 10:2–3, Daniel 10:12). Jesus continues the prayer to God initiated at his baptism (see Luke 3:21). In the wilderness he prays for Israel as a pious servant of God. He answers John’s call: Repent, for the kingdom of heaven is at hand
(Matthew 3:2). Just as he did not regard the baptism of John to be beneath him, so also he does not regard fasting and prayer to be too humiliating. These actions demonstrate his desire to be one with his people. This much is clear also from his hunger. Jesus shares in the weakness and the dependency of the natural human body. By concentrating on prayer, humans can rein in their desire for food for a long time, but they can never overcome that hunger.1
2 And after fasting forty days and forty nights, he was hungry.