Anuśāsana-parva Adhyāya 112: Dharma as the sole companion; karmic witnesses; rebirth sequences
Bṛhaspati–Yudhiṣṭhira Saṃvāda
अतीतेष्वनपेक्षा ये प्राप्तेष्वर्थेषु निर्ममा: । शौचमेव पर तेषां येषां नोत्पद्यते स्पृहा
Those who do not look back with longing to what has passed or been lost, who remain without possessive attachment to what has been gained, and in whose heart no craving arises at all—in them alone is found the highest purity.
भीष्म उवाच