Matsyapurana 171.20

171.20

yaṃ kālaṃ tau gatau muktau brahmā taṃ kālameva hi
tato ghoratamaṃ bhūyaḥ saṃśritaḥ paramaṃ vratam //

Brahmâ commenced again His rigid penances after Nârâyana and Kapila had left Him Then Brahmâ, in course of His practices, did not feel any comfort and happiness, for those [whom he had created] were single He created a beautiful woman from His body by virtue of His tapasya —20-21