Spotless devotees of the Lord have mentioned the source of such knowledge. How could one have knowledge of devotional service and detachment without the help of such devotees?
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
निमित्तानि च तस्येह प्रोक्तान्यनघ सूरिभिः । स्वतो ज्ञानं कुतः पुंसां भक्तिर्वैराग्यमेव वा
nimittāni ca tasyeha proktānyanagha sūribhiḥ | svato jñānaṃ kutaḥ puṃsāṃ bhaktirvairāgyameva vā
SB 3.7.39