Albert Barnes Commentary Psalms 141:3

"Set a watch, O Jehovah, before my mouth; Keep the door of my lips." — Psalms 141:3 (ASV)

Set a watch, O Lord, before my mouth — that I may not say anything rashly, imprudently, or improperly. . The prayer here is, that God would guard him from the temptation to say something wrong. He seems to have been prompted to this by the circumstances of the case and by the advice of those who were with him. See the introduction to the psalm. (Compare the notes at Psalms 11:1).

Keep the door of my lips — that my lips or mouth may not open except when it is proper and right; when something good and true is to be said. Nothing can be more proper than this prayer; nothing more desirable than that God should keep us from saying what we ought not to say.