I have been thinking about purity of heart and a few scriptures have come to my mind.
Matthew 5:8 — “Blessed are the pure in heart, for they shall see God.”
Psalm 24:3,4 — “Who may ascend the hill of the Lord? Who may stand in His holy place? He who has clean hands and a pure heart, who does not lift up his soul to an idol or swear by what is false.”
Psalm 51:10 — “Create in me a pure heart, O God, and renew a right spirit within me.”
I believe that purity is related to holiness. Hebrews 12:14 says “. . . without holiness no one will see the Lord.”
Someone who is pure in heart is a person whose thoughts and motives are blameless, someone who does not just do right things but who is also far from anything that defiles.
I also think of a pure diamond: when it is clean and pure, it can reflect light and cast around all kinds of color. When we are pure, then the light of God, when it shines on us, will be reflected in us and shine forth and all will see it and glorify the Lord.