Lord Nṛsiṁhadeva captured Hiraṇyakaśipu, who could not be pierced even by the thunderbolt of King Indra. He placed the demon on His lap, supporting him with His thighs, and in the doorway of the assembly hall the Lord very easily tore the demon to pieces with the nails of His hand. Hiraṇyakaśipu had received from Lord Brahmā the benediction that he would not die on the land or in the sky. Therefore, to keep the promise of Lord Brahmā intact, Nṛsiṁhadeva placed Hiraṇyakaśipu’s body on His lap, which was neither land nor sky. Hiraṇyakaśipu had received the benediction that he would not die either during the day or at night. Therefore, to keep this promise of Brahmā, the Lord killed Hiraṇyakaśipu in the evening, which is the end of day and the beginning of night but is neither day nor night. Hiraṇyakaśipu had taken a benediction from Lord Brahmā that he would not die from any weapon or be killed by any person, dead or alive. Therefore, just to keep the word of Lord Brahmā, Lord Nṛsiṁhadeva pierced Hiraṇyakaśipu’s body with His nails, which were not weapons and were neither living nor dead. Indeed, the nails can be called dead, but at the same time they can be said to be alive. To keep intact all of Lord Brahmā’s benedictions, Lord Nṛsiṁhadeva paradoxically but very easily killed the great demon Hiraṇyakaśipu.
Ref >> Srila Prabhupada Vani.