Caitanya-caritāmṛta 4.221
sei bhāve nija-vāñchā karila pūraṇa avatārera ei vāñchā mūla-kāraṇa
[sei bhaave nija-vaanchaa karila poorana avataarera ei vaanchaa moola-kaarana]
Blended reading (Sanskrit + English inline)
sei bhāve nija-vāñchā karila pūraṇa avatārera ei vāñchā mūla-kāraṇa
In the mood of Śrīmatī Rādhārāṇī, He also fulfilled His own desires. This is the principal reason for His appearance.
My note
Source: vedabase.io