King Yayati was completely aware of the duty of a ksatriya. When a ksatriya is approached by a woman, he cannot deny her. This is a religious principle. Consequently, when Dharmaraja, Yudhisthira, saw Arjuna unhappy after Arjuna returned from Dvaraka, he asked whether Arjuna had refused a woman who had begged for a son. Although Maharaja Yayati remembered Sukracaryas warning, he could not refuse Sarmistha. He thought it wise to give her a son, and thus he had sexual intercourse with her after her menstrual period. This kind of lust is not against religious principles. As stated in Bhagavad-gita (7.11), dharmaviruddho bhutesu kamo smi: sex life not contrary to the principles of religion is sanctioned by Krsna. Because Sarmistha, the daughter of a king, had begged Yayati for a son, their combination was not lust but an act of religion.