CC Madhya 22.158
siddha-rūpeṇa cātra hi
sevā — service; sādhaka-rūpeṇa — with the external body as a devotee practicing regulative devotional service; siddha-rūpeṇa — with a body suitable for eternal, self-realized service; ca — also; atra — in this connection; hi — certainly; tat — of that; bhāva — the mood; lipsunā — desiring to obtain; kāryā — to be executed; vraja-loka — of a particular servant of Kṛṣṇa in Vṛndāvana; anusārataḥ — by following in the footsteps.
“ ‘The advanced devotee who is inclined to spontaneous loving service should follow the activities of a particular associate of Kṛṣṇa’s in Vṛndāvana. He should execute service externally as a regulative devotee as well as internally from his self-realized position. Thus he should perform devotional service both externally and internally.’
This verse is also found in the Bhakti-rasāmṛta-sindhu (1.2.295).