CC Madhya 24.137
īśād apetasya viparyayo ’smṛtiḥ
tan-māyayāto budha ābhajet taṁ
bhayam — fear; dvitīya-abhiniveśataḥ — from the misconception of being a product of material energy; syāt — arises; īśāt — from the Supreme Personality of Godhead, Kṛṣṇa; apetasya — of one who has withdrawn (the conditioned soul); viparyayaḥ — reversal of position; asmṛtiḥ — no conception of his relationship with the Supreme Lord; tat-māyayā — because of the illusory energy of the Supreme Lord; ataḥ — therefore; budhaḥ — one who is wise; ābhajet — must worship; tam — Him; bhaktyā — by devotional service; ekayā — not diverted to karma and jñāna; īśam — the Supreme Personality of Godhead; guru — as the spiritual master; devatā — worshipable Lord; ātmā — Supersoul.
“ ‘When the living entity is attracted by the material energy, which is separate from Kṛṣṇa, he is overpowered by fear. Because he is separated from the Supreme Personality of Godhead by the material energy, his conception of life is reversed. In other words, instead of being the eternal servant of Kṛṣṇa, he becomes Kṛṣṇa’s competitor. This is called viparyayo ’smṛtiḥ. To nullify this mistake, one who is actually learned and advanced worships the Supreme Personality of Godhead as his spiritual master, worshipful Deity and source of life. He thus worships the Lord by the process of unalloyed devotional service.’
This verse is quoted from Śrīmad-Bhāgavatam (11.2.37).