CC Ādi 2.100

ei chaya-rūpe haya ananta vibheda
ananta-rūpe eka-rūpa, nāhi kichu bheda
Synonyms: 
ei — these; chaya-rūpe — in six forms; haya — there are; ananta — unlimited; vibheda — varieties; ananta-rūpe — in unlimited forms; eka-rūpa — one form; nāhi — there is not; kichu — any; bheda — difference.
Translation: 
“In these six kinds of forms there are innumerable varieties. Although they are many, they are all one: there is no difference between them.
Purport: 

The Personality of Godhead manifests Himself in six different features: (1) prābhava, (2) vaibhava, (3) empowered incarnations, (4) partial incarnations, (5) childhood and (6) boyhood. The Personality of Godhead Śrī Kṛṣṇa, whose permanent feature is adolescence, enjoys His transcendental proclivities by performing pastimes in these six forms. In these six features there are unlimited divisions of the Personality of Godhead’s forms. The jīvas, or living beings, are differentiated parts and parcels of the Lord. They are all diversities of the one without a second, the Supreme Personality of Godhead.