"Hiranyakasipu wanted to receive a benediction from Lord Brahma so that in the future he would be able to conquer Lord Brahma's abode. Similarly, another demon received a benediction from Lord Siva but later wanted to kill Lord Siva through that same benediction. Thus self-interested persons, by demoniac austerity, want to kill even their benedictors, whereas the Vaisnava wants to remain an ever-existing servant of the Lord and never to occupy the post of the Lord. Through sayujya-mukti, which is generally demanded by asuras, one merges into the existence of the Lord, but although one sometimes thus achieves the goal of the theory of monism, one falls down again to struggle in material existence."
Srimad-Bhagavatam 7:3:1 Purport
"Brahmaji declined to award him the benediction of immortality because he himself is not an immortal being. But Hiranyakasipu derived Brahmaji's benediction in a roundabout way, almost equal to becoming an immortal being. Hiranyakasipu was sure that he would not be killed by any man or demigod or by any kind of known weapon, nor would he die in day or night. The Lord, however, assumed the incarnation of half-man and half-lion, which was beyond the imagination of a materialistic demon like Hiranyakasipu, and thus, keeping pace with the benediction of Brahmaji, the Lord killed him. He killed him on His lap, so that he was killed neither on the land nor on the water nor in the sky. The demon was pierced by Nrsimha's nails, which were beyond the human weapons imaginable by Hiranyakasipu. The literal meaning of Hiranyakasipu is one who is after gold and soft bedding, the ultimate aim of all materialistic men. Such demonic men, who have no relationship with God, gradually become puffed up by material acquisitions and begin to challenge the authority of the Supreme Lord and torture those who are devotees of the Lord. Prahlada Maharaja happened to be the son of Hiranyakasipu, and because the boy was a great devotee, his father tortured him to the best of his ability. In this extreme situation, the Lord assumed the incarnation of Nrsimhadeva, and just to finish the enemy of the demigods, the Lord killed Hiranyakasipu in a manner beyond the demon's imagination. Materialistic plans of godless demons are always frustrated by the all-powerful Lord."
Srimad-Bhagavatam 2:7:14 Purport
"In Vedic culture, the welfare of the cows and the welfare of the brahmanas are essential. Without a proper arrangement for developing brahminical culture and protecting cows, all the affairs of administration will go to hell. Being afraid that Hiranyakasipu would occupy the post of Brahma, all the demigods were extremely disturbed. Hiranyakasipu was a well-known demon, and the demigods knew that if demons and Raksasas were to occupy the supreme post, brahminical culture and protection of cows would come to an end. As stated in Bhagavad-gita (5.29), the original proprietor of everything is Lord Krsna (bhoktaram yajna-tapasam sarva-loka-mahesvaram). The Lord, therefore, knows particularly well how to develop the material condition of the living entities within this material world. In every universe there is one Brahma engaged on behalf of Lord Krsna, as confirmed in Srimad-Bhagavatam (tene brahma hrdaya adi-kavaye). The principal creator in each brahmanda is Lord Brahma, who imparts Vedic knowledge to his disciples and sons. On every planet, the king or supreme controller must be a representative of Brahma. Therefore, if a Raksasa, or demon, were situated in Brahma's post, then the entire arrangement of the universe, especially the protection of the brahminical culture and cows, would be ruined. All the demigods anticipated this danger, and therefore they went to request Lord Brahma to take immediate steps to thwart Hiranyakasipu's plan."
Srimad-Bhagavatam 7:3:13 Purport
"Prahlada Maharaja, a small child of only five years, became the object of envy for his great father, Hiranyakasipu, only because of his becoming a pure devotee of the Lord. The demon father employed all his weapons to kill the devotee son, Prahlada, but by the grace of the Lord he was saved from all sorts of dangerous actions by his father. He was thrown in a fire, in boiling oil, from the top of a hill, underneath the legs of an elephant, and he was administered poison. At last the father himself took up a chopper to kill his son, and thus Nrsimhadeva appeared and killed the heinous father in the presence of the son."
Srimad-Bhagavatam 1:15:16 Purport
"Prahlada Maharaja was put into great distress by his powerful father, the demon Hiranyakasipu. Apparently helpless before him, Prahlada Maharaja called on the Lord, who immediately assumed the gigantic form of Nrsimhadeva, half-lion and half-man, to kill the gigantic demon. Although Krsna is the original person, one without a second, He assumes different forms just to satisfy His devotees or to execute a specific purpose."
Srimad-Bhagavatam 5:18:7 Purport
Bhaktivedanta Book Trust. Excerpted from texts and purports of HDG A.C. Bhaktivedanta Swami Srila Prabhupada.