קבלה אויף איכה 2:19

Arising after midnight:⁷²⁷To pray the Tikkun Chatzot prayer and to study Torah. Firstly, by engaging in this practice he is counted among those who mourn for Zion and Jerusalem, about which it states,⁷²⁸Isaiah 66:10 “Be glad in Jerusalem and rejoice in her, all you who love her, exult with her in jubilation, all you who mourn for her.” For, it is at that hour that the Holy One, blessed is He, also mourns and roars like a lion.⁷²⁹Talmud Bavli, Brachot 3a Moreover, in regard to one’s study of Torah at that hour, our sages, of blessed memory, stated,⁷³⁰Midrash Shemot Rabba 47:5; Vayikra Rabba 19:1 “The exaltation in the Torah is only at night.” Additionally, our sages, of blessed memory, stated,⁷³¹Talmud Bavli, Avoda Zarah 3b; Midrash Mishlei 31:3; Tanna d’Bei Eliyahu Zuta, Pirke Derech Eretz 2 “Whoever occupies himself with Torah study at night, the Holy One, blessed is He, extends a thread of kindness upon him by day.” Our sages, of blessed memory, also stated,⁷³²Talmud Bavli, Tamid 32b “Anyone who occupies himself with Torah study at night, the Indwelling Presence of HaShem-יהו״ה (the Shechinah), is opposite him. The verse states,⁷³³Lamentations 2:19 – In reference to Torah study (Shemot Rabba 47:5). “Arise! Exalt in the night, at the beginning of the watches!” King David, peace be upon him, only merited to live in this world and in the coming world on account of this practice,⁷³⁴Talmud Bavli, Brachot 3b-4a and elsewhere. as written,⁷³⁵Psalms 119:62 “At midnight I arise to thank You for Your righteous ordinances.” The book of Zohar is filled with explanations praising this mitzvah to no end, and the Holy Spirit of Divine Inspiration (Ru’ach HaKodesh) dwells upon such a person, as mentioned there in Parshat Shemot.⁷³⁶Zohar II 18b

However, if one studies during the day and he is satiated, he does not have to lengthen his study at night in a way that he cannot wake up at midnight. And “the wise man, his eyes are in his head” (Ecclesiastes 2:14) and will “order his affairs rightfully” (Psalms 112:5) in a way that he will deal with Torah during the day until he is satiated, and in the beginning of the night he will deal with Torah as well so that his soul can elevate by the breath of the Torah, but not to the point that he is satiated so he will not miss waking up at dawn, which is the main time to deal with Torah, as it says “Arise, cry out in the night, at the beginning of the watches [last part of the night]” (Lamentations 2:19).