Devibhagavatapurana 5.32.37

5.32.37

ṛṣiruvāca |
nirbhayaṃ vasa rājendra nātra te śatravaḥ kila |
āgamiṣyanti balino niścayaṃ tapaso balāt ||

The Maharsi said:-- “O King! Stay here without any fear; none of your enemies would be able to enter this hermitage by my power of Tapasyâ, even if they be very powerful. O Best of Kings! You will not be allowed to kill any animals here; you will have to sustain yourself on this wild rice, roots and fruits, etc., as the rules of the forest living permit.”