In Bhagavad-gītā (9.29) the Lord says:

samo ’haṁ sarva-bhūteṣu na me dveṣyo ’sti na priyaḥ ye bhajanti tu māṁ bhaktyā mayi te teṣu cāpy aham

The Supreme Personality of Godhead is undoubtedly equal to everyone. He has no friend and no enemy, but as one desires benefits from the Lord, the Lord is very pleased to award them. The lower and higher positions of different living entities are due to their desires, for the Lord, being equal to all, fulfills everyone’s desires. The killing of Hiraṇyakaśipu and saving of Prahlāda Mahārāja also strictly followed this law of the supreme controller’s activities. When Prahlāda’s mother, Hiraṇyakaśipu’s wife, Kayādhu, was under the protection of Nārada, she prayed for the protection of her son from the enemy, and Nārada Muni gave assurance that Prahlāda Mahārāja would always be saved from the enemy’s hands. Thus when Hiraṇyakaśipu was going to kill Prahlāda Mahārāja, the Lord saved Prahlāda to fulfill His promise in Bhagavad-gītā ( kaunteya pratijānīhi na me bhaktaḥ praṇaśyati ) and to prove true the words of Nārada. The Lord can fulfill many purposes through one action. Thus the killing of Hiraṇyakaśipu and the saving of Prahlāda were enacted simultaneously to prove the truthfulness of the Lord’s devotee and the fidelity of the Lord Himself to His own purpose. The Lord acts only to satisfy the desires of His devotees; otherwise He has nothing to do. As confirmed in the Vedic language, na tasya kāryaṁ karaṇaṁ ca vidyate: the Lord has nothing to do personally, for everything is done through His different potencies ( parāsya śaktir vividhaiva śrūyate ). The Lord has multifarious energies, through which everything is done. Thus when He personally does something, it is only to satisfy His devotee. The Lord is known as bhakta-vatsala because He very much favors His devoted servant.