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. Thus no one can kill the devotee of the Lord. "
Srimad-bhagavatam, 1:15:16 Purport
"Following the instructions of Prahlada Maharaja, all the sons of the demons became attached to Lord Visnu, the Supreme Personality of Godhead. When this attachment became pronounced, their teachers, Sanda and Amarka, were very much afraid that the boys would become more and more devoted to the Lord. In a helpless condition, they approached Hiranyakasipu and described in detail the effect of Prahlada's preaching. After hearing of this, Hiranyakasipu decided to kill his son Prahlada. Hiranyakasipu was so angry that Prahlada Maharaja fell down at his feet and said many things just to pacify him, but he was unsuccessful in satisfying his demoniac father. Hiranyakasipu, as a typical demon, began to advertise himself as being greater than the Supreme Personality of Godhead, but Prahlada Maharaja challenged him, saying that Hiranyakasipu was not God, and began to glorify the Supreme personality of Godhead, declaring that the Lord is all-pervading, that everything is under Him, and that no one is equal to or greater than Him. Thus he requested his father to be submissive to the omnipotent Supreme Lord.
The more Prahlada Maharaja glorified the Supreme personality of Godhead, the more angry and agitated the demon became. Hiranyakasipu asked his Vaisnava son whether his God existed within the columns of the palace, and Prahlada Maharaja immediately accepted that since the Lord is present everywhere, He was also present within the columns. When Hiranyakasipu heard this philosophy from his young son, he derided the boy's statement as just the talk of a child and forcefully struck the pillar with his fist.
As soon as Hiranyakasipu struck the column, there issued forth a tumultuous sound. At first Hiranyakasipu, the King of the demons, could not see anything but the pillar, but to substantiate Prahlada's statements, the Lord came out of the pillar in His wonderful incarnation as Narasimha, half lion and half man. Hiranyakasipu could immediately understand that the extraordinarily wonderful form of the Lord was surely meant for his death, and thus he prepared to fight with the form of half lion and half man. The Lord performed His pastimes by fighting with the demon for some time, and in the evening, on the border between day and night, the Lord captured the demon, threw him on His lap, and killed him by piercing his abdomen with His nails. The Lord not only killed Hiranyakasipu, the King of the demons, but also killed many of his followers. When there was no one else to fight, the Lord, roaring with anger, sat down on Hiranyakasipu's throne.
The entire universe was thus relieved of the rule of Hiranyakasipu, and everyone was jubilant in transcendental bliss. Then all the demigods, headed by Lord Brahma, approached the Lord. These included the great saintly persons, the Pitas, the Siddhas, the Vidyadharas, the Nagas, the Manus, the prajapatis, the Gandharvas, the Caranas, the Yaksas, the Kimpurusas, the Vaitalikas, the Kinnaras and also many other varieties of beings in human form. All of them stood not far from the Supreme Personality of Godhead and began offering their prayers unto the Lord, whose spiritual effulgence was brilliant as He sat on the throne."
Srimad-bhagavatam, 7:8 Summary
"Prahlada Maharaja, while praying to Lord Nrsimha, said, "O my Lord, I am very much afraid of the materialistic way of life, and I am not the least afraid of Your present ghastly ferocious feature as Nrsimhadeva. This materialistic way of life is something like a grinding stone, and we are being crushed by it. We have fallen into this horrible whirlpool of the tossing waves of life, and thus, my Lord, I pray at Your lotus feet to call me back to Your eternal abode as one of Your servitors. This is the summit liberation of this materialistic way of life. I have very bitter experience of the materialistic way of life. In whichever species of life I have taken birth, compelled by the force of my own activities, I have very painfully experienced two things, namely separation from my beloved and meeting with what is not wanted. And to counteract them, the remedies which I undertook were more dangerous than the disease itself. So I drift from one point to another birth after birth, and I pray to You therefore to give me a shelter at Your lotus feet."
Srimad-bhagavatam 1:19:20 Purport
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.