CC Madhya 20.108-109

jīvera ‘svarūpa’ haya — kṛṣṇera ‘nitya-dāsa’
kṛṣṇera ‘taṭasthā-śakti’ ‘bhedābheda-prakāśa’
sūryāṁśa-kiraṇa, yaiche agni-jvālā-caya
svābhāvika kṛṣṇera tina-prakāra ‘śakti’ haya
Word for word: 
jīvera — of the living entity; svarūpa — the constitutional position; haya — is; kṛṣṇera — of Lord Kṛṣṇa; nitya-dāsa — eternal servant; kṛṣṇera — of Lord Kṛṣṇa; taṭasthā — marginal; śakti — potency; bheda-abheda — one and different; prakāśa — manifestation; sūrya-aṁśa — part and parcel of the sun; kiraṇa — a ray of sunshine; yaiche — as; agni-jvālā-caya — molecular particle of fire; svābhāvika — naturally; kṛṣṇera — of Lord Kṛṣṇa; tina-prakāra — three varieties; śakti — energies; haya — there are.
Translation: 
“It is the living entity’s constitutional position to be an eternal servant of Kṛṣṇa because he is the marginal energy of Kṛṣṇa and a manifestation simultaneously one with and different from the Lord, like a molecular particle of sunshine or fire. Kṛṣṇa has three varieties of energy.
Purport: 

Śrīla Bhaktivinoda Ṭhākura explains these verses as follows: Śrī Sanātana Gosvāmī asked Śrī Caitanya Mahāprabhu, “Who am I?” In answer, the Lord replied, “You are a pure living entity. You are neither the gross material body nor the subtle body composed of mind and intelligence. Actually you are a spirit soul, eternally part and parcel of the Supreme Soul, Kṛṣṇa. Therefore you are His eternal servant. You belong to Kṛṣṇa’s marginal potency. There are two worlds — the spiritual world and the material world — and you are situated between the material and spiritual potencies. You have a relationship with both the material and the spiritual world; therefore you are called the marginal potency. You are related with Kṛṣṇa as one and simultaneously different. Because you are spirit soul, you are one in quality with the Supreme Personality of Godhead, but because you are a very minute particle of spirit soul, you are different from the Supreme Soul. Therefore your position is simultaneously one with and different from the Supreme Soul. The examples given are those of the sun itself and the small particles of sunshine and of a blazing fire and the small particles of fire.” Another explanation of these verses can be found in Ādi-līlā, chapter two, verse 96.