Mahabharata 12.220.65
शोककाले शुचो मा त्वं हर्षकाले च मा हृषःअतीतानागते हित्वा प्रत्युत्पन्नेन वर्तय
śokakāle śuco mā tvaṃ harṣakāle ca mā hṛṣaḥatītānāgate hitvā pratyutpannena vartaya
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book