Caitanya-caritāmṛta 24.172
sādhanaughair anāsaṅgair alabhyā su-cirād api hariṇā cāśv adeyeti dvidhā sā syāt su-durlabhā
[saadhanaughair anaasangair alabhyaa su-chiraad api harinaa chaashv adeyeti dvidhaa saa syaat su-durlabhaa]
Blended reading (Sanskrit + English inline)
sādhanaughair anāsaṅgair alabhyā su-cirād api hariṇā cāśv adeyeti dvidhā sā syāt su-durlabhā
“ ‘Devotional perfection is very difficult to attain for two reasons. First, unless one is attached to Kṛṣṇa, he cannot attain devotional perfection even if he renders devotional service for a long time. Second, Kṛṣṇa does not easily deliver perfection in devotional service.’
Purport
As stated in Śrīmad-Bhāgavatam (5.6.18), muktiṁ dadāti karhicit. Śrīla Śukadeva Gosvāmī told Mahārāja Parīkṣit that Kṛṣṇa readily grants liberation but does not very readily grant perfection in devotional service. This means that Kṛṣṇa wants to see that a devotee is actually sincere and serious and that he does not have ulterior motives. If this is the case, devotional service can very easily be successful; otherwise it is very difficult to obtain from the Supreme Personality of Godhead. This verse appears in the Bhakti-rasāmṛta-sindhu (1.1.35).
— A.C. Bhaktivedanta Swami Prabhupāda
My note
Source: vedabase.io