An ascetic should wake up in Brahma Muhurta and meditate on one's Guru

संन्यासाचारवर्णनं नाम चतुर्थोऽध्यायः

Renunciation behaviour description Chapter 4

ईश्वर उवाच |

God said (to supreme Goddess Parvati)

ब्राह्मे मुहूर्ते उत्थाय शिरसि श्वेतपङ्कजे |
सहस्रारे समासीनं गुरुं सञ्चिन्तयेद्यतिः || 2 ||

An ascetic should wake up in Brahma muhurta (96 to 48 minutes before sunrise), (and) think of (or meditate on one's) Guru sitting on the white lotus of the Sahasrara (chakra on the crown) of the head.