Matthew 5:8, “Blessed are the pure in heart, for they shall see God.”
This is not a conditional statement in that if we have pure actions and intentions, we will be saved and therefore see God, because we are not saved by works. Christ alone makes us pure. “And everyone who thus hopes in Him purifies himself as He is pure” (1 John 3:3). Because of our faith in Christ, He purifies our hearts for His sake. St. Augustine likewise said, “A pure heart… is a single heart: and just as this light cannot be seen, except with pure eyes; so neither is God seen, unless that is pure by which He can be seen” (A Select Library of Nicene and Post-Nicene Fathers of the Christian Church, Series 1, 6:5). Thus, the pure in heart are those who do not worship false gods but the one and only God, YHWH. And so, as believers, God makes us holy and pure through sanctification in baptism so that when Jesus returns, we will stand before Him totally pure. As we have purified hearts by faith in Christ, He enables us to act with pure hearts. In Luther’s words, “It is easily told, and you need not climb to heaven nor run into a monastery after it and make it out with your own thoughts; but be guarded against all such thoughts as you call your own, as against so much mud and filth” (61). With purified hearts, the Holy Spirit enables us to guard ourselves against our evil, impure thoughts. When we are tempted into sexual perversion, the Holy Spirit gives us the power to reject those urges. When we are tempted to lie, the Holy Spirit gives us the power to tell the truth. In essence, with our purified hearts from Christ, the Holy Spirit gives us the power to overcome sin, an ability that cannot be done without Him.
And so because Christ purifies our hearts by faith for His sake, we shall see God.
Luther, Martin. Commentary on the Sermon on the Mount, translated by Charles A. Hay. Philadelphia: Lutheran Publication Society, 1892.
Source used from Logos 7 Software.