Set a Guard Over My Mouth

Set a guard over my mouth, Lord;
    keep watch over the door of my lips.

Do not let my heart be drawn to what is evil
    so that I take part in wicked deeds
along with those who are evildoers;
    do not let me eat their delicacies. 

Let a righteous man strike me - that is a kindness;
    let him rebuke me - that is oil on my head.
My head will not refuse it,
    for my prayer will still be against the deeds of evildoers.

(Psalm 141:3-5)