PURPORT

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