If we say we have no sin, we deceive ourselves. 1 John 1:8
Purity of heart does not mean you never have a bad thought. Christians in this life are always sinners in the process of recovery, and if purity of heart meant you never have a bad thought, it would be a blessing that no Christian could ever receive.
The Bible speaks about purity in different ways and it is important to distinguish between them:
Purity that belongs to God alone. In the presence of God, the holy angels, who have never sinned, cover their faces and cry out, “Holy, holy, holy is the LORD of hosts” (Isa. 6:3). It isn’t enough for them to say that God is holy, but that He is holy, holy, holy. The angels are holy, but God is incomparable in His purity. His holiness is the source of theirs. Like the angels, we will reflect the holiness of God forever as the moon reflects the light of the sun. But the light of holiness is His alone and any holiness in us comes from Him.
Purity that will be ours in heaven. “When he appears we shall be like him, because we shall see him as he is” (1 John 3:2). In the presence of Jesus, you will have a purity that is like pure gold. There will not be a trace of sin in you, on you, or around you.
Purity that we must pursue now. “Blessed are the pure in heart…” (Matt. 5:8). Thomas Watson describes this mixture of grace and sin in our Christian lives as “purity in a gospel sense… as a face may be said to be fair which has some freckles in it.” Where there is a longing for purity and a loathing of impurity, there is purity of heart.
What’s the difference between God’s purity and yours? How does knowing this help you?