SB 7.3.21
tatas ta asisah sarva
dadamy asura-pungava
martasya te hy amartasya
darsanam naphalam mama
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
O best of the asuras, for this reason I am now prepared to give you all benedictions, according to your desire. I belong to the celestial world of demigods, who do not die like human beings. Therefore, although you are subject to death, your audience with me will not go in vain.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It appears that human beings and asuras are subject to death, whereas demigods are not. The demigods who reside with Lord Brahma in Satyaloka go to Vaikunthaloka in their present bodily constructions at the time of the dissolution. Therefore although Hiranyakasipu had undergone severe austerities, Lord Brahma predicted that he had to die; he could not become immortal or even gain equal status with the demigods. The great austerities and penances he had performed for so many years could not give him protection from death. This was foretold by Lord Brahma.