He was a great emperor and possessed all the opulences of his acquired kingdom. He was so exalted that he was increasing the prestige of the Pāṇḍu dynasty. Why did he give up everything to sit down on the bank of the Ganges and fast until death?
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स सम्राट् कस्य वा हेतोः पाण्डूनां मानवर्धनः । प्रायोपविष्टो गङ्गायामनादृत्याधिराट् श्रियम्
sa samrāṭ kasya vā hetoḥ pāṇḍūnāṃ mānavardhanaḥ | prāyopaviṣṭo gaṅgāyāmanādṛtyādhirāṭ śriyam
SB 1.4.10