There are three original deities - Brahma, Visnu and Mahesvara. Hiranyakasipu knew that Brahma would not kill him, but he also wanted not to be killed by Lord Visnu or Lord Siva. Consequently, he prayed for such a benediction

Expressions researched:
"There are three original deities" |"Brahmā, Viṣṇu and Maheśvara. Hiraṇyakaśipu knew that Brahmā would not kill him, but he also wanted not to be killed by Lord Viṣṇu or Lord Śiva. Consequently, he prayed for such a benediction"

Srimad-Bhagavatam

SB Canto 7

There are three original deities - Brahma, Visnu and Mahesvara. Hiranyakasipu knew that Brahma would not kill him, but he also wanted not to be killed by Lord Visnu or Lord Siva. Consequently, he prayed for such a benediction.

SB 7.3.36, Translation and Purport

Grant me that I not die within any residence or outside any residence, during the daytime or at night, nor on the ground or in the sky. Grant me that my death not be brought by any being other than those created by you, nor by any weapon, nor by any human being or animal.

Hiraṇyakaśipu was very much afraid of Viṣṇu's becoming an animal to kill him because his brother had been killed by Viṣṇu when the Lord took the shape of a boar. He was therefore very careful to guard against all kinds of animals. But even without taking the shape of an animal, Viṣṇu could kill him by hurling His Sudarśana cakra, which can go anywhere without the Lord's physical presence. Therefore Hiraṇyakaśipu was careful to guard against all kinds of weapons. He guarded against all kinds of time, space and countries because he was afraid of being killed by someone else in another land. There are many other planets, higher and lower, and therefore he prayed for the benediction of not being killed by any resident of any of these planets. There are three original deities—Brahmā, Viṣṇu and Maheśvara. Hiraṇyakaśipu knew that Brahmā would not kill him, but he also wanted not to be killed by Lord Viṣṇu or Lord Śiva. Consequently, he prayed for such a benediction. Thus Hiraṇyakaśipu thought himself securely protected from any kind of death caused by any living entity within this universe. He also carefully guarded against natural death, which might take place within his house or outside of the house.