Psalm 17:3-9 You have tried my heart, you have visited me by night, you have tested me, and you will find nothing; I have purposed that my mouth will not transgress. 4 With regard to the works of man, by the word of your lips I have avoided the ways of the violent. 5 My steps have held fast to your paths; my feet have not slipped. 6 I call upon you, for you will answer me, O God; incline your ear to me; hear my words. 7 Wondrously show your steadfast love, O Savior of those who seek refuge from their adversaries at your right hand. 8 Keep me as the apple of your eye; hide me in the shadow of your wings, 9 from the wicked who do me violence, my deadly enemies who surround me. (ESV)
Unlike David, I dare not say that God has tested me and found "nothing"--that is, no sin. I can only say that God has tested me and allow me to confess all my sins so that I may be cleansed. Jesus says, "Blessed are the pure in heart, for they shall see God." Thankfully, the word "pure" is katharos in Greek, meaning "cleansed" rather than sinless as the English word implies. We are pure because we have confessed our sins daily before God as the Spirit convicts us -- and the cleansing comes with the confession: "If we confess our sins, God is faithful and just and will forgive us and purify (cleanse-katharos) us from all unrighteousness" (1 John 1:9). Only in that sense can we say with David: "You have tried my heart... you have tested me, and you will find nothing!" because the Blood of Christ has removed every trace of sin in our heart as we confess them before God!
So how do we know we have a cleansed/purified heart? David suggests a few indicators:
(1) PURE SPEECH: "I have purposed that my mouth will not transgress." When our heart is cleansed, our speech reflects it. Jesus has said in Matthew 12:34, "For out of the abundance of the heart the mouth speaks."
(2) RIGHTEOUS CONDUCT: "I have avoided the ways of the violent. My steps have held fast to your paths; my feet have not slipped." Not only in speech, but a pure heart is revealed in our right conduct -- one that is consistent with God's ways ("my steps have held fast to your paths"). Violent or aggressive behaviour is inconsistent with a cleansed heart.
(3) ANSWERED PRAYERS: "I call upon you, for you will answer me": Those who are pure in heart "shall see God." Here Jesus cannot mean seeing God literally ("no one shall see God and live"--only the dead see God literally!). But we can see God in His acts - in His answers to our prayers. So, the pure in heart shall see God acting on their behalf as they cry out to Him in their prayers.
Father, we thank You that when You search and test us, You find nothing because all our sins have been removed (cleansed) by the Blood of Christ. So, now keep our speech and conduct pure - and let us see You in Your action on our behalf! Amen.