CC Ādi 4.121

tāṅhāra prathama vāñchā kariye vyākhyāna
kṛṣṇa kahe, — ‘āmi ha-i rasera nidāna
Word for word: 
tāṅhāra — His; prathama — first; vāñchā — desire; kariye — I do; vyākhyāna — explanation; kṛṣṇa — Lord Kṛṣṇa; kahe — says; āmi — I; ha-i — am; rasera — of mellow; nidāna — primary cause.
Translation: 
I shall explain His first desire. Kṛṣṇa says, “I am the primary cause of all rasas.