Prahlada's nine forms of devotion: hearing of Vishnu, singing His glories, remembering Him, serving His feet, worshipping Him, prostrating, regarding oneself as His servant, befriending Him, and full self-surrender.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
श्रवणं कीर्तनं विष्णोः स्मरणं पादसेवनम्। अर्चनं वन्दनं दास्यं सख्यमात्मनिवेदनम्॥
śravaṇaṁ kīrtanaṁ viṣṇoḥ smaraṇaṁ pāda-sevanam arcanaṁ vandanaṁ dāsyaṁ sakhyam ātma-nivedanam
SB 7.5023