Jaiminīya Upaniṣad Brāhmaṇa 1.2.7

1.2.7

yad u ha vā āpaḥ parācīr eva prasṛtās syanderan kṣīyeraṁs tāḥ
yad aṅkāṁsi kurvāṇā niveṣṭamānā āvartān sṛjamānā yanti kṣayād eva bibhyatīḥ
tad etad vāyoś caivāpāṃ cānu vartma geyam /
prathame 'nuvāke dvitīyaḥ khaṇḍaḥ //

And if the waters were to flow only straight away, they would perish.
When they flow making bends, twisting about, creating whirlpools, it is out of fear of perishing.
Therefore it should be sung following the path of the wind and the waters.
Second khaṇḍa in the first anuvāka.