Rudra-prasava-varṇana
The Manifestation and Naming of Rudra / Nīlalohita
न चैताः परिचक्षीत वहन्त्यो वा स्थिता अपि / मैध्यामेध्यास्त्वपामेतास्तनवो मुनिभिः स्मृताः
na caitāḥ paricakṣīta vahantyo vā sthitā api / maidhyāmedhyāstvapāmetāstanavo munibhiḥ smṛtāḥ
And do not regard these waters—whether flowing or still—with a fault-finding gaze; for the sages have taught that the forms of water are held to be both pure and, at times, impure.