Devibhagavatapurana 7.36.28

7.36.28

anyathā tu kṛtaghnaḥ syātkṛtaghne nāsti niṣkṛtiḥ |
indreṇātharvaṇāyoktā śiraśchedapratijñayā ||

O Best of Mountains! It is very difficult to acquire Brahma Jñâna. Hear a story. A Muni named Dadhyam of Atharvana family went to Indra and prayed to him to give Brahma Jñâna. Indra said: "I would give you Brahma-Jñâna, but if you impart it to any other body, I would sever your head." Dadhyarna agreed to this and Indra gave him the Brahma-Jñâna. After a few days, the two As'vins came to the Muni and prayed for Brahma Vidyâ, The Muni said:-- "If I give you the Brahma-Vidyi, Indra, will cut off my head." Hearing this the two As'vins said:-- "We will cut your head and keep it elsewhere and we will attach the head of a horse to your body. Instruct us with the mouth of this horse and when Indra will cut off your this mouth, we will replace your former head." When they said so, the Muni gave them the Brahma-Vidyâ. Indra cut off his head by his thunderbolt. When the horse-head of the Muni was cut off, the two physicians of the Devas replaced his original head. This is widely known in all the Vedas.
O Chief of Mountains! He becomes blessed who gets this the Brahma-Vidyâ.
Here ends theThirty-sixth Chapter of the Seventh Book on the Highest Knowledge of Brahma in the Mahapurânam, S'rî Mad Devî Bhâgavatam, of 18,000 verses, by Maharsi Veda Vyâsa.