Srimad Bhagavatam Canto 10, Chapter 01, Text 24

SB 10.1.24

vasudeva-kalanantah
sahasra-vadanah svarat
agrato bhavita devo
hareh priya-cikirsaya
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The foremost manifestation of Krsna is Sankarsana, who is known as Ananta. He is the origin of all incarnations within this material world. Previous to the appearance of Lord Krsna, this original Sankarsana will appear as Baladeva, just to please the Supreme Lord Krsna in His transcendental pastimes.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Sri Baladeva is the Supreme Personality of Godhead Himself. He is equal in supremacy to the Supreme Godhead, yet wherever Krsna appears, Sri Baladeva appears as His brother, sometimes elder and sometimes younger. When Krsna appears, all His plenary expansions and other incarnations appear with Him. This is elaborately explained in Caitanya-caritamrta. This time, Baladeva would appear before Krsna as Krsna’s elder brother.
Srimad Bhagavatam Canto 10, Chapter 01, Text 23
Srimad Bhagavatam Canto 10, Chapter 01, Text 25