How can a man be free of guile, falsehood, and wickedness since the scripture reveals that blessed are the pure in heart for they shall see God?

There are two things to understand concerning this question,

~1~ A man can NEVER be free from guile, falsehood, and wickedness, since the state of man in the flesh is unsalvageable!

"The flesh", even as it remains in the believer after salvation, is that which is "begotten [birthed] of the flesh" (John 3:6) from parent to child tracing all the way back to Adam by whom "Sin entered the world" (Romans 5:12). It is called, "the flesh," "the old man," "the natural man," "the carnal mind" and "the old Adamic nature".

With respect to "the flesh" in the believer, the Apostle Paul declares that in it "dwells no good thing" (Romans 7:18), that it is "carnal, sold under sin" (Romans 7:14), that it is "corrupt according to the deceitful lusts" (Ephesians 4:22), that it is at "enmity against God," and it is "not subject to the law of God, neither indeed can be" (Romans 8:7). Just as "they that are in the flesh cannot please God" (Romans 8:8) so that which is of the flesh, in the believer, cannot please God. "The flesh" is totally depraved. God calls it "sinful flesh" (Romans 8:3), warns that it seeks "occasion" to do wrong (Galatians 5:13), and declares that "the works of the flesh" are all debased [polluted, corrupted, infected, defiled] (Galatians 5:19-21). The acts of the flesh are filthy rags (Isaiah 64:6) before the God.

The flesh cannot be fixed. It cannot be changed. The old nature in the believer does not, will not and cannot improve and therefore cannot be salvaged. It is completely corrupt, spoilt to the core and irreparable; to the point that the only way to deal with it is that it be replaced with a new incorruptible nature (1 Corinthians 15:53).

~2~ The way to be FREE from guile, falsehood, and wickedness, is to DIE to the flesh and be regenerated as a NEW ‘spirit’ man!

Concerning salvation:

Realize off the bat that your regenerated spirit man that is quickened to life at salvation is FREE from sin and guilt!!!! Our sins are nailed to the cross and Christ’s righteousness is imputed to us so that we are seen as pure, whole, and perfect, in the eyes of God. This is the absolute undiluted grace of God tto us through Christ. You see, salvation by the grace gospel does this ALL for us. It is done for us by Christ! We don’t lift a finger to earn this status or position! This is how we die to the flesh and get regenerated into a new creature. This is our eternal state in Christ.

But what about the flesh and what about now, here on earth? How do I live now to please God?

Concerning the flesh:

The "old Adamic nature" was condemned and dealt with judicially (and with finality) at the Cross. Never once is the believer instructed in the Word to try to do anything with or to make anything of the flesh (the old man). Why? Because it is completely corrupt and irreparable. The Word tells us to "reckon [count] it dead indeed" (Romans 6:11, Galatians 2:20), and to "put it off" (Colossians 3:8-10).

Do we try and manage it? Do we try to train it? Do we force it to adhere to us by punishing it, but suppressing it, but isolating it? No. Even if we did, it would not help a single bit as sin is inside the nature of man and it cannot be controlled. So, how do we deal with the flesh?

In a word, "put it off" is "sanctification", the process by which the Holy Spirit works in the lives of God's redeemed to grow them and form them into the image of God's one and only Son, Jesus Christ. Sanctification is God's will for our lives (1 Thessalonians 4:3), and it is a purpose to which He has called us (Romans 8:29). It is not our effort to live a holy life! No. It is the work of the Spirit within us, convicting us and gently urging us to wise up and choose right.

Realize that we as believers know and must admit that we still on occasion commit ‘acts of the Sin nature’ (‘sin’ is located “in the flesh” of our physical body (Rom. 8:3b) … even after we have been saved.) To deny this is to deny our daily reality.

Note that we never did anything to effectively be saved and we are not required to do anything to remain saved… however, if we have genuinely believed and received the Lord as our Saviour by faith, then we will have a growing sense of appreciation and love for the Lord. This appreciation and a growing love for the Lord comes as we begin to understand the details of what He has done for us...but studying the Bible. His love extended to us will eventually run its course and ‘constrain our heart’ to want to walk in union with Him and the will of His indwelling “spirit of life” (Rom. 8:2a). His indwelling “Spirit” inwardly convicts our hearts of wrongdoing and wrong thinking, motivating us toward living righteous lives.