[ source ]
Matthew 4:2 And he [Jesus] fasted forty days and forty nights, and afterward he was hungry.
Matthew 6:16-18 And when you fast, do not look dismal, like the hypocrites, for they disfigure their faces that their fasting may be seen by men. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by men but by your Father who is in secret; and your Father who sees in secret will reward you.
Matthew 9:14-15 Then the disciples of John came to him, saying, "Why do we and the Pharisees fast, but your disciples do not fast?" And Jesus said to them, "Can the wedding guests mourn as long as the bridegroom is with them? The days will come, when the bridegroom is taken away from them, and then they will fast." (cf. Mk 2:18-20; Lk 5:33-35; 18:12)
Luke 1:15 for he will be great before the Lord, and he shall drink no wine nor strong drink, and he will be filled with the Holy Spirit, even from his mother's womb.
Luke 2:37 . . . She did not depart from the temple, worshiping with fasting and prayer night and day.
Luke 7:33 For John the Baptist has come eating no bread and drinking no wine; and you say, 'He has a demon.' (cf. Mt 11:18)
Acts 13:2-3 While they were worshiping the Lord and fasting, the Holy Spirit said, "Set apart for me Barnabas and Saul for the work to which I have called them." Then after fasting and praying they laid their hands on them and sent them off.
Acts 14:23 And when they had appointed elders for them in every church, with prayer and fasting they committed them to the Lord in whom they believed.
Acts 15:20 . . . abstain from the pollutions of idols and from unchastity and from what is strangled and from blood.
Acts 15:29 . . . abstain from what has been sacrificed to idols and from blood and from what is strangled and from unchastity. . . . (cf. 21:25)
Romans 14:3 Let not him who eats despise him who abstains, and let not him who abstains pass judgment on him who eats; for God has welcomed him.
Romans 14:6 He who observes the day, observes it in honor of the Lord. He also who eats, eats in honor of the Lord, since he gives thanks to God; while he who abstains, abstains in honor of the Lord and gives thanks to God.
Romans 14:15,21 If your brother is being injured by what you eat, you are no longer walking in love. Do not let what you eat cause the ruin of one for whom Christ died. . . . it is right not to eat meat or drink wine or do anything that makes your brother stumble.
1 Corinthians 8:13 Therefore, if food is a cause of my brother's falling, I will never eat meat, lest I cause my brother to fall.
2 Corinthians 6:4-5 but as servants of God we commend ourselves in every way: through great endurance, in afflictions, hardships, calamities, beatings, imprisonments, tumults, labors, watching, hunger;
2 Corinthians 11:27 in toil and hardship, through many a sleepless night, in hunger and thirst, often without food, in cold and exposure.
As for the forty days of Lent, The Catholic Encyclopedia: "Lent" (subcategory: "Duration of the Fast") states:
In determining this period of forty days the example of Moses, Elias, and Christ must have exercised a predominant influence, but it is also possible that the fact was borne in mind that Christ lay forty hours in the tomb. On the other hand just as Pentecost (the fifty days) was a period during which Christians were joyous and prayed standing, though they were not always engaged in such prayer, so the Quadragesima (the forty days) was originally a period marked by fasting, but not necessarily a period in which the faithful fasted every day.Much more on this is in the article. The New Bible Dictionary (edited by J.D. Douglass, Grand Rapids, MI: Eerdmans, 1962, "Number" (p. 898 for the following quotation) brings out many interesting aspects of "forty":
Forty is associated with almost each new development in the history of God's mighty acts, especially of salvation, e.g., the flood, redemption from Egypt, Elijah and the prophetic era, the advent of Christ, and the birth of the Church. The following periods of forty days may be listed: the downpour of rain during the flood (Gn. 7:17); the despatch of the raven (Gn. 8:6); Moses' fasts on the mount (Ex. 24:18, 34:28; Dt. 9:9); the spies' exploration of the land of Canaan (Nu. 13:25); Moses' prayer for Israel (Dt. 9:25); Goliath's defiance (1 Sa. 17:16); Elijah's journey to Horeb (1 Ki. 19:8); Ezekiel's lying on his right side (Ezk. 4:6); Jonah's warning to Nineveh (Jon. 3:4); Christ's stay in the wilderness prior to His temptation (Mt. 4:2), His appearances after His resurrection (Acts 1:3).There are several more incidences of the duration of 40 years (the Jews' wandering in the wilderness, reigns of the great kings, etc.), but I'll pass on typing all those, since the immediate analogy is to the 40 days of Lent.