Adam Clarke's Commentary on the Bible

Verse 172 (Psalms 119:172)

My tongue shall speak of thy word - There is a curious distinction here. In the preceding verse he says, "My lips shall utter;" here no reference is made to articulate sounds, except as affixed to musical notes. In this verse he says, "My tongue shall speak;" here articulate and intelligible words are intended. He first utters sounds connected with words expressive of his grateful feelings; in the second he speaks words, principally those which God himself had spoken, containing promises of support, purposes relative to the redemption of his people, and denunciations against their enemies.

- Adam Clarke's Commentary on the Bible