of David = by David, and relating to the true David. The Psalm is a continuation of the subject of this last group of four Psalms. Psa_39:2:9 link it on to Psa_38:13; and Psa_39:1 to Psa_38:17. See note on Title of Psa_38:1.
I said = I formed this resolution (Psa_38:7).
take heed = observe, keep, or guard.
sin. Hebrew. chata'.App-44.
keep: same as "take heed to", above. Septuagint and Vulgate read "I did put".
a bridle = a muzzle.
the wicked = a lawless one. Hebrew. rasha'.App-44.