SB 7.4.43

tasmin mahā-bhāgavate
 mahā-bhāge mahātmani
hiraṇyakaśipū rājann
 akarod agham ātmaje
tasmin — unto him; mahā-bhāgavate — an exalted devotee of the Lord; mahā-bhāge — most fortunate; mahā-ātmani — whose mind was very broad; hiraṇyakaśipuḥ — the demon Hiraṇyakaśipu; rājan — O King; akarot — performed; agham — very great sin; ātma-je — to his own son.
My dear King Yudhiṣṭhira, the demon Hiraṇyakaśipu tormented this exalted, fortunate devotee, although Prahlāda was his own son.

When a demon like Hiraṇyakaśipu, despite his elevated position due to severe austerities, begins to tease a devotee, he begins falling down, and the results of his austerities dwindle. One who oppresses a pure devotee loses all the results of his austerities, penances and pious activities. Since Hiraṇyakaśipu was now inclined to chastise his most exalted devotee son, Prahlāda Mahārāja, his opulences began dwindling.