Psalm 141 is another instance of David crying out to the LORD in prayer. At the heart of this prayer is David’s desire that the LORD keep him from doing evil, with the focus on his tongue and his heart.
Set a guard, O LORD, over my mouth; keep watch over the door of my lips.
Do not incline my heart to any evil thing, to practice deeds of wickedness with men who do iniquity; and do not let me eat of their delicacies (vv. 3-4).
If there is one thing that sets the godly man apart, it’s the recognition that he is not godly in himself; thus he prays to the Lord to sanctify him – to keep him from sins that offend God and others. And where better (and more convicting) to begin than with the potential for sin with our tongue. I can think of too many times when I wish I had prayed: Lord, set a guard over my mouth! As it says in Proverbs:
The one who guards his mouth preserves his life; the one who opens wide his lips comes to ruin (13:3).
When there are many words, transgression is unavoidable, but he who restrains his lips is wise (10:19).
Likewise, the Spirit speaks through James of the relationship of the tongue to our sanctification:
For we all stumble in many ways. If anyone does not stumble in what he says, he is a perfect man, able to bridle the whole body as well (James 3:2).
Yet as Jesus said, even what comes out of our mouths is really a reflection of what is in our hearts: “…for his mouth speaks from that which fills his heart” (Luke 6:45). No wonder David prayed at the end of Psalm 139: “Search me, O God, and know my heart!” That is where I need to begin: O God, search my heart – and change my heart to be more like You!