Likutei Halakhot, Orach Chaim, Laws of Morning Hand Washing 2:3/ליקוטי הלכות·אורח חיים·הלכות נטילת ידים שחרית ב׳:ג׳

1Therefore one must rise at midnight to break sleep, to break the aspect of darkness and night, which is the aspect of the exile, which resembles the night; in other words, the knowledge of natural science from which is the essence of the exile and the darkness, as explained above. Every Jew must awaken from sleep at midnight in order to break and nullify the knowledge of nature through breaking the sleep, etc., as explained above. Then, when one rises at midnight, one mourns over the exile which drove Israel from our land. For the essence of the exile is through the knowledge of natural science, which corresponds to night and sleep, as explained above. Therefore, that is the time to rectify this.