SB 6.11.21
aham samadhaya mano yathaha nah
sankarsanas tac-caranaravinde
tvad-vajra-ramho-lulita-gramya-paso
gatim muner yamy apaviddha-lokah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
By the force of your thunderbolt, I shall be freed of material bondage and shall give up this body and this world of material desires. Fixing my mind upon the lotus feet of Lord Sankarsana, I shall attain the destination of such great sages as Narada Muni, just as Lord Sankarsana has said.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The words aham samadhaya manah indicate that the most important duty at the time of death is to concentrate one’s mind. If one can fix his mind on the lotus feet of Krsna, Visnu, Sankarsana or any Visnu murti, his life will be successful. To be killed while fixing his mind at the lotus feet of Sankarsana, Vrtrasura asked Indra to release his vajra, or thunderbolt. He was destined to be killed by the thunderbolt given by Lord Visnu; there was no question of its being baffled. Therefore Vrtrasura requested Indra to release the thunderbolt immediately, and he prepared himself by fixing his mind at the lotus feet of Krsna. A devotee is always ready to give up his material body, which is described herein as gramya-pasa, the rope of material attachment. The body is not at all good; it is simply a cause of bondage to the material world. Unfortunately, even though the body is destined for destruction, fools and rascals invest all their faith in the body and are never eager to return home, back to Godhead.