Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 10

Sanskrit:

द्रव्यभूयोवरेणापस्तुरीयं जगृहुर्मलम् ।तासु बुद्बुदफेनाभ्यां द‍ृष्टं तद्धरति क्षिपन् ॥ १० ॥

ITRANS:

dravya-bhūyo-vareṇāpasturīyaṁ jagṛhur malamtāsu budbuda-phenābhyāṁdṛṣṭaṁ tad dharati kṣipan

Translation:

And in return for King Indra’s benediction that water would increase the volume of other substances with which it was mixed, water accepted one fourth of the sinful reactions. Therefore there are bubbles and foam in water. When one collects water, these should be avoided.

Purport:

If water is mixed with milk, fruit juice or other similar substances, it increases their volume, and no one can understand which has increased. In return for this benediction, water accepted one fourth of Indra’s sinful reactions. These sinful reactions are visible in foam and bubbles. Therefore one should avoid foam and bubbles while collecting drinking water.