Mateus 4

Mateus 4:2

So you see, my friends, the fact that we fast during Lent is not of human invention. The authority is divine and mystical and not taken for granted. Nor is it based on an earthly custom but on heavenly secrets. Lent [Quadragesima] contains the four-sided teaching of four decades of faith, because perfection is always four-sided. The number forty [quadragesimus] and the number ten [denarius], which hold sacraments both in heaven and on earth because a square is not free to open, are used to explain the undertaking of the Lord's fast. — SERMONS 11.4