CC Ādi 5.25

ei tina loke kṛṣṇa kevala-līlā-maya
nija-gaṇa lañā khele ananta samaya
Word for word: 
ei — these; tina — three; loke — in the locations; kṛṣṇa — Lord Kṛṣṇa; kevala — only; līlā-maya — consisting of pastimes; nija-gaṇa lañā — with His personal associates; khele — He plays; ananta samaya — unlimited time.
Translation: 
Only in these three places [Dvārakā, Mathurā and Gokula] does the all-sporting Lord Kṛṣṇa perform His endless pastimes with His personal associates.