Matsya Purana 48.57

48.57

kāṣṭhe samudre prakṣipya gaṅgāmbhasi samutsṛjat.
yasmāttvamandhovṛddhaśca bharttavyoduradhiṣṭhitaḥ.. 48.57 ..

With those words, she packed him in a wooden case and threw him into the Ganges, saying, "I abandon you (and do not kill you, pitying) your blindness and old age."—57.