Charak Samhita
उदीर्यते भृशतरं मार्गरोधाद्वहज्जलम् । यथा तथाऽनिलस्तस्य मार्गं नित्यं विशोधयेत् ॥१२२॥
If the path of flowing water is blocked the enhancing pressure of water breaks the dam similarly the path obstructed by kapha aggravates vata and causes harm, hence always the path of vayu should be cleaned by means of purification.
english translation
udIryate bhRzataraM mArgarodhAdvahajjalam । yathA tathA'nilastasya mArgaM nityaM vizodhayet ॥122॥
hk transliteration by Sanscript