You tested my heart and examined me in the night. You refined me with fire and found no unrighteousness in me. I have purposed in my mind that my mouth will not transgress.
David entrusts his heart with confidence to God’s examination. The words “You have tested my heart” show that the Lord examines not only a person’s outward conduct, but also his inner thoughts and motives. The phrase “You examined me in the night” further emphasizes the depth of that examination: in the silence of the night, when outward noise grows quiet, a person can more clearly see the true condition of his heart and bring it sincerely before God. The image “You refined me with fire” recalls the testing of metal, when its true quality is revealed through fire. The words “You found no unrighteousness in me” refer to the matter at hand and do not mean that David considers himself completely innocent. He is confident that God’s examination will not find in him the deceit and sinful intent of which he is being accused. At the end of the verse David also says that he has resolved not to transgress with his mouth. This thought is especially important in a time of trial, when a person can easily sin with words—by lying, insulting, or resorting to unjust means in order to defend his own cause. David wants his righteousness to be seen not only in the intention of his heart, but also in his speech. This verse reminds the believer that the desire to be righteous before God begins from within. The Lord examines the heart, exposes motives, and also pays attention to speech. Therefore, in a moment of hardship and injustice, it is important not only to see the other person’s fault, but also to keep one’s own heart and speech upright and straight before the Lord.