When the Personality of Godhead, Mohinī-mūrti, severed Rāhu's head from his body, the head remained alive although the body died. Rāhu had been drinking nectar through his mouth, and before the nectar entered his body, his head was cut off. Thus Rāhu's head remained alive whereas the body died. This wonderful act performed by the Lord was meant to show that nectar is miraculous ambrosia.
Śrīmad-Bhāgavatam 8.9.25, Purport
