Because of the vrata he followed-nrsimha said to prahlada -due to being attached to a prostitute you became accustomed to drinking wine and performing other sinful activities, so that you never engaged in the study of the vedas. you spent more time at the house of the prostitute. one day however you and she quarrelled with each other and because of that you missed your meal that day. as a result both of you unknowingly observed a sacred vow in relation with me not eating and sleeping the entire day and through the night.because of unknowingly observing this vow in relation to me, you became purified and accumulated heaps of pious merit. by the performance of this vow many devas, brahma and mahadeva attained perfection of life and the power they needed to perform their tasks. dear prahlada, on the strength of that vow you came to render devotional service unto me. in the next life the prostitute was born in heaven as an apsara and after enjoying life there she entered my supreme abode.