Set a watch, O LORD, before my mouth; keep the door of my lips.
Set a watch, O Lord, before my mouth ... Incline not my heart to any evil thing, to practice wicked works - (cf. Psalms 119:36.) God, in judicial retribution, gives up the froward to their evil inclinations. The heart is the fountain of evil. We need to pray God not to 'lead us into temptation,' by judicial reprobation (James 1:13-14; Matthew 6:13). In Psalms 141:3 he prays for preservation from sin of tongue; in Psalms 141:4, from sin of deed. Psalms 39:1-2 is a commentary, on Psalms 141:3. He feels tempted by his own trials, and by the prosperity of the enemy, to utter impatient complaints against God, and even to apostatize to the practices of the wicked (cf. Ps. 37:49,73): this, therefore, he prays against. In Psalms 141:5-7 he calls to remembrance the reasons which should keep him from such murmurings, and from joining the wicked in their practices-namely, that the faithful reproofs and chastisements administered by righteous men (the instruments of the righteous God) are far preferable to the dainties of the wicked; and that the overthrow of the rulers of the wicked is coming, though now Israel's bones lie scattered at the grave's mouth.
Keep the door of my lips - (Micah 7:5.)
Verse 4. To practice wicked works with men that work iniquity. Unless the inclination of the will be resisted in time, it goes on to "practice wicked work."
And let me not eat of their dainties - let me not be allured into joining them in sin, through their seeming prosperity in and by it. As here their prosperity is represented under the image of delicious, dainties, so in Psalms 73:10, under the image of "waters of a full cup wrung out to them" (cf. Proverbs 23:6).