Mahabharata — Anushasana Parva, Shloka 1196
ज्येष्ठ-कनिष्ठ-धर्मः — Duties of Elders and Juniors
Anuśāsana-parva 108
पानीयस्य क्रिया नक्तं न कार्या भूतिमिच्छता । अपना कल्याण चाहनेवाले पुरुषको रातमें श्राद्धकर्म नहीं करना चाहिये। भोजन करके केशोंका संस्कार (क्षौरकर्म) भी नहीं करना चाहिये तथा रातमें जलसे स्नान करना भी उचित नहीं है
pānīyasya kriyā naktaṃ na kāryā bhūtim icchatā |
毗湿摩说道：“求福祉与兴盛之人，不应在夜间行与饮水相关之仪。”依于正行（ācāra）之戒，凡净化与祭仪之事——尤以施罗陀（śrāddha）之礼、饭后修整身体如剃刮理发（kṣaura），以及夜间以水沐浴——皆当于夜里避之，以求吉祥安泰。
भीष्म उवाच
Educational Q&A
The verse teaches ācāra: a person seeking auspicious welfare (bhūti) should avoid certain prescribed rites at night—here, specifically the ‘pānīya-kriyā’ (a ritual/procedural act connected with drinking-water), implying that timing and propriety are integral to dharma.
In Anuśāsana Parva, Bhīṣma instructs Yudhiṣṭhira on dharma and proper conduct. This verse is part of that didactic sequence, giving a rule about what should not be done at night for one aiming at auspicious well-being.