SB 9.18.41

turvasuś coditaḥ pitrā
 druhyuś cānuś ca bhārata
pratyācakhyur adharmajñā
 hy anitye nitya-buddhayaḥ
Synonyms: 
turvasuḥ — Turvasu, another son; coditaḥ — requested; pitrā — by the father (to exchange old age and invalidity for his youth); druhyuḥ — Druhyu, another son; ca — and; anuḥ — Anu, another son; ca — also; bhārata — O King Parīkṣit; pratyācakhyuḥ — refused to accept; adharma-jñāḥ — because they did not know religious principles; hi — indeed; a-nitye — temporary youth; nitya-buddhayaḥ — thinking to be permanent.
Translation: 
O Mahārāja Parīkṣit, Yayāti similarly requested his sons Turvasu, Druhyu and Anu to exchange their youth for his old age, but because they were unaware of religious principles, they thought that their flickering youth was eternal, and therefore they refused to carry out their father’s order.