For ten days Śrī Caitanya Mahāprabhu stayed at Prayāga and instructed Rūpa Gosvāmī, empowering him with the necessary potency.
This is a confirmation of the statement kṛṣṇa-śakti vinā nahe tāra pravartana. Unless one is specifically empowered by the Supreme Personality of Godhead, he cannot spread the Kṛṣṇa consciousness movement. An empowered devotee sees and feels himself to be the lowest of men, for he knows that whatever he does is due to the inspiration given by the Lord in the heart. This is confirmed by Lord Kṛṣṇa in the Bhagavad-gītā (BG 10.10):
dadāmi buddhi-yogaṁ taṁ
yena mām upayānti te
"To those who are constantly devoted to serving Me with love, I give the understanding by which they can come to Me."
To be empowered by the Supreme Personality of Godhead, one has to qualify himself. This means that one must engage twenty-four hours daily in the loving devotional service of the Lord. The material position of a devotee doesn’t matter because devotional service is not dependent on material considerations. In his earlier life, Śrīla Rūpa Gosvāmī was a government officer and a gṛhastha. He was not even a brahmacārī or sannyāsī. He associated with mlecchas and yavanas, but because he was always eager to serve, he was a qualified recipient for the Lord’s mercy. A sincere devotee can therefore be empowered by the Lord regardless of his situation. In the preceding verse from the Bhakti-rasāmṛta-sindhu, Śrīla Rūpa Gosvāmī has described how he was personally empowered by the Lord. He further states in the Bhakti-rasāmṛta-sindhu (1.2.187):
īhā yasya harer dāsye
karmaṇā manasā girā
nikhilāsv apy avasthāsu
jīvan-muktaḥ sa ucyate
"A person acting in the service of Kṛṣṇa with his body, mind and words is a liberated person even in the material world, although he may be engaged in many so-called material activities."
To keep oneself free from material contamination and attain the Lord’s favor, one must be sincerely eager to render service to the Lord. This is the only qualification necessary. As soon as one is favored by the mercy of the spiritual master and the Lord, one is immediately given all the power necessary to write books and propagate the Kṛṣṇa consciousness movement without being hampered by material considerations.
(Caitanya-caritāmṛta Madhya 19.135, Translation and Purport)