Balaram Purnima
Balarāma appeared with Him as Lord Nityānanda.
(CC Adi 5.6)
The foremost manifestation of Kṛṣṇa is Saṅkarṣaṇa, who is known as Ananta. He is the origin of all incarnations within this material world. Previous to the appearance of Lord Kṛṣṇa, this original Saṅkarṣaṇa will appear as Baladeva, just to please the Supreme Lord Kṛṣṇa in His transcendental pastimes.
(SB 10.1.24)
Balarāma is considered to be the elder brother of Kṛṣṇa. When Kṛṣṇa was present, Balarāma became His elder brother. When Rāma was there, this Balarāma represented Himself as His younger brother, Lakṣmaṇa. So Balarāma is the first manifestation of His personal expansion.
(661216 – Lecture CC Madhya 20.172-244 – New York)
Playing like a bull, Lord Balarāma fights with Kṛṣṇa head to head. And sometimes Lord Kṛṣṇa massages the feet of Lord Balarāma. He considers Himself a servant and knows Kṛṣṇa to be His master. Thus He regards Himself as a fragment of His plenary portion.
(CC Adi 5.136 – 5.137)
Because Mahā-saṅkarṣaṇa is the ingredient and efficient cause of the cosmic manifestation, He is present in every detail of it. Lord Caitanya therefore called Him His elder brother. The two brothers are known as Kṛṣṇa and Balarāma in the spiritual world, but at the present moment they are Caitanya and Nitāi. Therefore the conclusion is that Nityānanda Prabhu is the original Saṅkarṣaṇa, Baladeva.
(CC Adi 13.78)
(3) Lord Krishna, who is the son of the King of Vraja, became the son of Saci (Lord Caitanya), and Balarama became Nitai. The holy name delivered all those souls who were lowly and wretched. The two sinners Jagai and Madhai are evidence of this.
(Hari Hari Biphale Janama)