SB 6.12.35
vrtrasya dehan niskrantam
atma-jyotir arindama
pasyatam sarva-devanam
alokam samapadyata
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O King Pariksit, subduer of enemies, the living spark then came forth from Vrtrasura’s body and returned home, back to Godhead. While all the demigods looked on, he entered the transcendental world to become an associate of Lord Sankarsana.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Srila Visvanatha Cakravarti Thakura explains that Indra, not Vrtrasura, was actually killed. He says that when Vrtrasura swallowed King Indra and his carrier, the elephant, he thought, “Now I have killed Indra, and therefore there is no more need of fighting. Now let me return home, back to Godhead.” Thus he stopped all his bodily activities and became situated in trance. Taking advantage of the silence of Vrtrasura’s body, Indra pierced the demon’s abdomen, and because of Vrtrasura’s trance, Indra was able to come out. Now, Vrtrasura was in yoga-samadhi, and therefore although King Indra wanted to cut his throat, the demon’s neck was so stiff that Indra’s thunderbolt took 360 days to cut it to pieces. Actually it was the body left by Vrtrasura that was cut to pieces by Indra; Vrtrasura himself was not killed. In his original consciousness, Vrtrasura returned home, back to Godhead, to become an associate of Lord Sankarsana. Here the word alokam means the transcendental world, Vaikunthaloka, where Sankarsana eternally resides.
Thus end the Bhaktivedanta purports of the Sixth Canto, Twelfth Chapter, of the Srimad-Bhagavatam, entitled “Vrtrasura’s Glorious Death.”