Numbers in the Bible are very important because they are symbolic. For instance, whenever the number 3 appears in the Bible it usually has a Trinitarian aspect. The number 7 represents perfection. In Genesis, God rested on the 7th day because He had finished the work of creation and saw that everything was good (Genesis 1). One less than 7 is 6 which represents imperfection, hence why the devil's number in the book of Revelation is 666 (Revelation 13:18). 12 represents the tribes of Israel.
The number 40, however, refers to a time of penance. This is why the Church has her members celebrate Lent for 40 days. One of the greatest instances of 40 days of penance in the Bible is when Moses goes up to Mt. Sinai to speak with God and receive the Ten Commandments (Exodus 24:28) A second example comes from the Gospel of Matthew (see Matthew 4:1-11). Before Jesus sets out upon His ministry, He spends 40 days fasting and praying in the wilderness.
What is the significance then of these biblical accounts? In the example of Moses, we see that in order to prepare himself to converse intimately with God and receive the Ten Commandments “He neither ate bread nor drank water” (Exodus 34:18). His mortifications helped him
While Jesus is fasting and praying in the wilderness, the devil comes to tempt Him. We are told that Jesus was hungry after fasting for 40 days (Matt. 4:2) The devil tells Him to use His power and indulge in food, to indulge in pleasure, to satisfy the passions. He asks “If you are the Son of God, command these stones to become bread.” (Matt. 4:3) Jesus of course being God cannot sin, but He is the prime example for us. The devil tempts us in the same way. The devil tells us to indulge in our passions, in too much food, in bad habits, to indulge in sin. It is through His fasting and mortifications that He is able to reject the temptations of Satan.
So too, we, must fast, pray, and give alms in order to reject the temptations of the devil. This is why the Church has the season of Lent to recall the great victory Christ has won for us over the Prince of the World. The season of Lent helps us strengthen ourselves with God's grace through mortifications and prayer in order that we too may be victorious over the temptations of the Enemy.
St. Peter warns us in his epistle: “Stay sober and alert. Your opponent the devil is prowling like a roaring lion, looking for someone to devour. Resist him solid in your faith.” (1 Peter 5:8-9) Mortifications like fasting and almsgiving can be difficult but are worthwhile in the end. Venerable Fulton J. Sheen would say that mortifications are not the ends but the means to the end. Our end goal is union with God in Heaven. Prayer, fasting, and almsgiving during the season of Lent are sure ways of working toward that Goal.