SB 8.9.25
cakrena ksura-dharena
jahara pibatah sirah
haris tasya kabandhas tu
sudhayaplavito ’patat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Supreme Personality of Godhead, Hari, using His disc, which was sharp like a razor, at once cut off Rahu’s head. When Rahu’s head was severed from his body, the body, being untouched by the nectar, could not survive.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
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.