Matsyapurana 25.56

25.56

putro bhūtvā niṣkramasvodarānme bhittvā kukṣiṃ jīvaya māṃ ca tāta
avekṣethā dharmavatīmavekṣāṃ guroḥ sakāśātprāpya vidyāṃ savidyaḥ //

Śukra said:—“O, son of Bṛihaspati! who is prized by Devayânî, become a seer and acquire my sañjîvanî knowledge for I am assured now that you are not Indra in the disguise of Kacha. Because none excepting a Brâhmaṇa can live in my stomach, and Indra being a Kṣatriya would have been digested by me. Therefore learn this science from me. Come out of my stomach as my son, *i.e.*, first acquire the sañjîvanî knowledge and then come out of my stomach after ripping it open and restore me to life and then satisfy the expectation of this dutiful daughter of mine, after having mastered this science from me, thy guru." 54-56.