Mbh 1.64.3a

“Vaisampayana said, ‘It hath been heard by us, O monarch, that what thou askest is a mystery even to the gods. I shall, however, speak of it unto thee, after bowing down (to the self-born). The son of Jamadagni (Parasurama), after twenty-one times making the earth bereft of Kshatriyas wended to that best of mountains Mahendra and there began his ascetic penances. And at that time when the earth was bereft of Kshatriyas, the Kshatriya ladies, desirous of offspring, used to come, O monarch, to the Brahmanas and Brahmanas of rigid vows had connection with them during the womanly season alone, but never, O king, lustfully and out of season. And Kshatriya ladies by thousands conceived from such connection with Brahmanas. Then, O monarch, were born many Kshatriyas of greater energy, boys and girls, so that the Kshatriya race, might thrive. And thus sprang the Kshatriya race from Kshatriya ladies by Brahmanas of ascetic penances. And the new generation, blessed with long life, began to thrive in virtue. And thus were the four orders having Brahmanas at their head re-established. And every man at that time went in unto his wife during her season and never from lust and out of season. And, O bull of the Bharata race, in the same way, other creatures also, even those born in the race of birds went in unto their wives during the season alone. And, O protector of the earth, hundreds of thousands of creatures were born, and all were virtuous and began to multiply in virtue, all being free from sorrow and disease. And, O thou of the elephant’s tread, this wide earth having the ocean for her boundaries, with her mountains and woods and towns, was once more governed by the Kshatriyas. And when the earth began to be again governed virtuously by the Kshatriyas, the other orders having Brahmanas for their first were filled with great joy. And the kings giving up all vices born of lust and anger and justly awarding punishments to those that deserved them protected the earth.