CC Ādi 9.11

śrī-īśvarapurī-rūpe aṅkura puṣṭa haila
āpane caitanya-mālī skandha upajila
Word for word: 
śrī-īśvara-purī — by the name Śrī Īśvara Purī; rūpe — in the form of; aṅkura — the seed; puṣṭa — cultivated; haila — became; āpane — Himself; caitanya-mālī — the gardener of the name Śrī Caitanya Mahāprabhu; skandha — trunk; upajila — expanded.
Translation: 
The seed of devotional service next fructified in the form of Śrī Īśvara Purī, and then the gardener Himself, Caitanya Mahāprabhu, became the main trunk of the tree of devotional service.
Purport: 

Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura writes in his Anubhāṣya, “Śrī Īśvara Purī was a resident of Kumārahaṭṭa, where there is now a railroad station known as Kāmarhaṭṭa. Nearby there is another station, named Hālisahara, which belongs to the Eastern Railway. This railway runs from the eastern section of Calcutta.”

Īśvara Purī appeared in a brāhmaṇa family and was the most beloved disciple of Śrīla Mādhavendra Purī. In the last portion of Śrī Caitanya-caritāmṛta (Antya 8.28-31), it is stated:

īśvara-purī gosāñi kare śrī-pada sevana
sva-haste karena mala-mūtrādi mārjana

nirantara kṛṣṇa-nāma karāya smaraṇa
kṛṣṇa-nāma kṛṣṇa-līlā śunāya anukṣaṇa

tuṣṭa hañā purī tāṅre kaila āliṅgana
vara dilā kṛṣṇe tomāra ha-uka prema-dhana

sei haite īśvara-purī premera sāgara

“At the last stage of his life Śrī Mādhavendra Purī became an invalid and was completely unable to move, and Īśvara Purī so completely engaged himself in his service that he personally cleaned up his stool and urine. Always chanting the Hare Kṛṣṇa mahā-mantra and reminding Śrī Mādhavendra Purī about the pastimes of Lord Kṛṣṇa in the last stage of his life, Īśvara Purī gave the best service among his disciples. Thus Mādhavendra Purī, being very pleased with him, blessed him, saying, ‘My dear boy, I can only pray to Kṛṣṇa that He will be pleased with you.’ Thus Īśvara Purī, by the grace of his spiritual master, Śrī Mādhavendra Purī, became a great devotee in the ocean of love of Godhead.” Śrīla Viśvanātha Cakravartī states in his Gurv-aṣṭaka prayer, yasya prasādād bhagavat-prasādo yasyāprasādān na gatiḥ kuto ’pi: “By the mercy of the spiritual master one is blessed by the mercy of Kṛṣṇa. Without the grace of the spiritual master one cannot make any advancement.” It is by the mercy of the spiritual master that one becomes perfect, as vividly exemplified here. A Vaiṣṇava is always protected by the Supreme Personality of Godhead, but if he appears to be an invalid, this gives a chance to his disciples to serve him. Īśvara Purī pleased his spiritual master by service, and by the blessings of his spiritual master he became such a great personality that Lord Caitanya Mahāprabhu accepted him as His spiritual master.

Śrīla Īśvara Purī was the spiritual master of Śrī Caitanya Mahāprabhu, but before initiating Lord Caitanya he went to Navadvīpa and lived for a few months in the house of Gopīnātha Ācārya. At that time Lord Caitanya became acquainted with him, and it is understood that he served Śrī Caitanya Mahāprabhu by reciting his book, Kṛṣṇa-līlāmṛta. This is explained in Śrī Caitanya-bhāgavata, Ādi-khaṇḍa, chapter eleven.

To teach others by example how to be a faithful disciple of one’s spiritual master, Śrī Caitanya Mahāprabhu, the Supreme Personality of Godhead, visited the birthplace of Īśvara Purī at Kumāra-haṭṭa and collected some earth from his birth site. This He kept very carefully, and He used to eat a small portion of it daily. This is stated in the Caitanya-bhāgavata, Ādi-khaṇḍa, chapter seventeen. It has now become customary for devotees, following the example of Śrī Caitanya Mahāprabhu, to go there and collect some earth from that place.