PURPORT

In Bhagavad-gita sexual intercourse for begetting children is accepted as righteous. A person sexually inclined for simple sense gratification, however, is unrighteous. In Diti's appeal to her husband for sex, it was not exactly that she was afflicted by sex desires, but she desired sons. Since she had no sons, she felt poorer than her co-wives. Therefore Kasyapa was supposed to satisfy his bona fide wife.