Matsyapurana 124.110

124.110

ābhūtasamplavasthānām amṛtatvaṃ vibhāvyate
trailokyasthitikālo hi na punarmāragāmiṇām //

The seven Ṛiṣis desiring progeny took birth in the age of Dwâpara and conquered death, as they despised the work of propagating children. 88000 Ṛiṣis have gone into the path of those seven Ṛiṣis by becoming Ūrdhareta (perpetual celebates). They will live till the destruction of the world on the northern path of the sun. They became immortal as by their example they taught the people the sacrifice of lust, passion, likes and dislikes, abstaining from procreation, and other worldly enjoyment, by showing their worthlessness. Those who remain till the end of the universe are called immortals. They exist so long as the three worlds exist. Not so the mortals who follow the path of the Mâra, such as lust, great sins like the slaying of embryonic cells and great virtues like the performance of Aśwamedha yajña (Horse sacrifice). The immortals or the Ūrdharetas go into unconciousness at the time of the dissolution of the universe, and not before.—106-110.