Even though it is a mitzvah to study during the day and at night, it is only at night that a person acquires most of his wisdom. Therefore, a person who desires to merit the crown of Torah should be careful with all his nights, not giving up even one to sleep, eating, drinking, talk, or the like. Rather, [they should be devoted to] the study of Torah and the words of wisdom.
Our Sages declared: "The song of Torah can [be heard] only at night, as [Eichah 2:19] states: 'Arise, sing out at night...’“
Whoever occupies himself with Torah study at night will have a strand of [Divine] favor extended over him during the day, as [implied by Psalms 42:9]: "During the day, God ordains His kindness and, at night, His song is with me, a prayer to the living God."
[In contrast], any house in which the words of Torah cannot be heard at night will be consumed by fire, as [implied by Job 20:26]: "All the darkness is hidden away from His treasures; a fire that need not be blown will consume him."
[The verse, Numbers 16:31,] "He scorned the word of God," applies to someone who pays no attention to Torah at all. Similarly, anyone who has the potential to occupy himself with Torah study and does not, or who has studied both the Written and Oral Law and turned away to the vanities of the world, leaving behind his study and ignoring it, is included in the category of "those who scorn the word of God."
Our Sages declared: "Whoever neglects Torah study when wealthy will ultimately neglect it amidst poverty. Whoever maintains the Torah in poverty will ultimately maintain it amidst prosperity." This concept is explicitly mentioned in the Torah [Deuteronomy 28:47-48], which states: "Because you did not serve God, your Lord, with happiness and good feeling when there was an abundance of everything, you shall serve your enemies," and [Deuteronomy 8:16] states: "so that you shall suffer...so that ultimately He will make you prosper."