SB 10.16.1

śrī-śuka uvāca
vilokya dūṣitāṁ kṛṣṇāṁ
 kṛṣṇaḥ kṛṣṇāhinā vibhuḥ
tasyā viśuddhim anvicchan
 sarpaṁ tam udavāsayat
Word for word: 
śrī-śukaḥ uvāca — Śrī Śukadeva Gosvāmī said; vilokya — seeing; dūṣitām — contaminated; kṛṣṇām — the river Yamunā; kṛṣṇaḥ — Lord Śrī Kṛṣṇa; kṛṣṇa-ahinā — by the black serpent; vibhuḥ — the almighty Lord; tasyāḥ — of the river; viśuddhim — the purification; anvicchan — desiring; sarpam — serpent; tam — that; udavāsayat — sent away.
Translation: 
Śukadeva Gosvāmī said: Lord Śrī Kṛṣṇa, the Supreme Personality of Godhead, seeing that the Yamunā River had been contaminated by the black snake Kāliya, desired to purify the river, and thus the Lord banished him from it.