srstva caracaram idam
tad aham vardhamanena
kalatmanos ca nityatvat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
“The supreme person within this universe, Lord Brahma, has gotten his exalted post by dint of severe austerities, mystic power and trance. Consequently, after creating the universe, he has become the most worshipable demigod within it. Since I am eternal and time is eternal, I shall endeavor for such austerity, mystic power and trance for many, many births, and thus I shall occupy the same post occupied by Lord Brahma.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Hiranyakasipu’s determination was to occupy the post of Lord Brahma, but this was impossible because Brahma has a long duration of life. As confirmed in Bhagavad-gita (8.17), sahasra-yuga-paryantam ahar yad brahmano viduh: one thousand yugas equals one day of Brahma. The duration of Brahma’s life is extremely great, and consequently it was impossible for Hiranyakasipu to occupy that post. Nonetheless, his decision was that since the self (atma) and time are both eternal, if he could not occupy that post in one lifetime he would continue to execute austerities life after life so that sometime he would be able to do so.