Mbh 9.43.1b

' Then all those Brahmanas, O king, worshipping Mahadeva, that lord of the universe and protector of all creatures, with penance and vows and fasts and diverse kinds of abstinences and painful observances, emancipated that foremost of rivers, the divine Sarasvati. Beholding the water of Sarasvati purified by those Munis, the Rakshasas (that had taken up their abode there), afflicted with hunger, sought the protection of those Munis themselves. Afflicted with hunger, the Rakshasas, with joined hands, repeatedly said unto those ascetics filled with compassion, these words, 'All of us are hungry! We have swerved from eternal virtue! That we are sinful in behaviour is not of our free will! Through the absence of your grace and through our own evil acts, as also through the sexual sins of our women, our demerits increase and we have become Brahma-Rakshasas! So amongst Vaisyas and Sudras, and Kshatriyas, those that hate and injure Brahmanas became Rakshasas. Ye best of Brahmanas, make arrangements then for our relief! Ye are competent to relieve all the worlds!' Hearing these words of theirs, those ascetics praised the great river. For the rescue of those Rakshasas, with rapt minds those ascetics said, 'The food over which one sneezed, that in which there are worms and insects, that which may be mixed with any leavings of dishes, that which is mixed with hair, that which is mixed with tears, that which is trodden upon shall form the portion of these Rakshasas! The learned man, knowing all this, shall carefully avoid these kinds of food. He that shall take such food shall be regarded as eating the food of Rakshasas!' Having purified the tirtha in this way, those ascetics thus solicited that river for the relief of those Rakshasas. Understanding the views of those great Rishis, that foremost of rivers caused her body, O bull among men, to assume a new shape called Aruna.