"Holiness begins with a pure heart free of lust and the law of sin and death."
Holiness is separation, the quality of being separate. However your definition doesn't hold true to scripture.
How does a person claiming Christ reject having a pure heart??
Who shall ascend into the hill of the LORD? or who shall stand in his holy place? He that hath clean hands, and a pure heart.
Now the end of the commandment is charity out of a pure heart, and of a good conscience, and of faith unfeigned:
Flee also youthful lusts: but follow righteousness, faith, charity, peace, with them that call on the Lord out of a pure heart.
When God told Moses to remove his sandals because he was standing on holy ground. The ground had no inherent purity, but was made holy by God's presence. Objects and people are sanctified by their use and purpose, not by their nature.
This of course is an open rejection of being born of the Spirit with the new divine nature of Christ: it is a confession of remaining the old man of sinful character, a soul unwashed and cleansed of all unrighteousness by the blood of the Lamb.
This is a person trying to live in an unwashed OT relationship with the God of Israel, while claiming NT salvation of the resurrected Saviour Jesus Christ: sanctified to God as 'chosen', but not inwardly sanctified by the Spirit.
And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
Holiness is not defined by purity.
So, God's holiness is not pure nor is it defined by purity, but is only a physical placement of purpose: this is the error of the unbelieving Pharisees who trusted only in washing of tables as holiness to the Lord, and sought nothing of God's pure holiness inwardly.
Man's false holiness is defined only by 'situational' purpose, but to say God's true holiness is not being pure and holy as he is holy, is a lie of the devil, that any normal uncorrupted child would reject.
First there is personal faith without works of God, and now there is holiness of God without purity of heart: being holiness unto the Lord while remaining unclean of soul and impure of heart.
A separation unto God for personal salvation, without being saved and separated from the sins and trespasses of the world.
Sanctify yourselves therefore, and be ye holy: for I am the LORD your God.
In the OT, this command only pertained to outer washings and services of a worldly tabernacle (Heb 9:1), but with the precious blood of Christ and the Lamb without spot, this commandment is to be fulfilled wholly and holy within by the Spirit and Word of God:
But as he which hath called you is holy, so be ye holy in all manner of conversation; Because it is written, Be ye holy; for I am holy.
Calvin's predestination 'of who' also rejects 'what': to be conformed to His image of righteousness and true holiness.
It results in a profane teaching of OT unwashed souls and hearts trying to claim NT salvation, based solely upon personal belief in being prechosen before birth, while openly rejecting a pure heart and going on still in their unrepented sins and trespasses.
The personally think they are already preknown, predestinated, prechosen, and presecured for eternal salvation, once they 'believe it'.
And they only treat predestination of being conformed to His image, as a matter of 'want to':
The Lord wants us to be of good character, but we aren't holy because of our character, but in spite of it.
They think themselves by foolish faith to be eternally secured with salvation by prechoosing of God, despite continuing in unholy character and unrighteous living.
They literally think themselves prechosen and 'separated' unto God for salvation, without being sanctified inwardly of the Spirit and separated from all unrighteousness of the world: not born of the Spirit, circumcised of heart in Christ, nor made a wholly new creature with the holy divine nature of God's perfect seed.
Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God.