CC Madhya 22.97

vijña-janera haya yadi kṛṣṇa-guṇa-jñāna
anya tyaji’, bhaje, tāte uddhava — pramāṇa
Word for word: 
vijña-janera — of an experienced person; haya — there is; yadi — if; kṛṣṇa-guṇa-jñāna — knowledge of Kṛṣṇa’s transcendental qualities; anya — others; tyaji’ — giving up; bhaje — he engages in devotional service; tāte — in that connection; uddhava — Uddhava; pramāṇa — the evidence.
Translation: 
“Whenever an experienced person develops real knowledge of Kṛṣṇa and His transcendental qualities, he naturally gives up all other engagements and renders service to the Lord. Uddhava gives evidence concerning this.