“Blessed are the pure in heart: for they shall see God.”
Matthew 5:8 — Greek Interlinear
Church Fathers on Matthew 5:8
The merciful loses the benefit of his mercy, unless he shews it from a pure heart; for if he seeks to have whereof to boast, he loses the fruit of his deeds; the next that follows therefore is, 'Blessed are the pure of heart.'
Purity of heart comes properly in the sixth place, because on the sixth day man was created in the image of God, which image was shrouded by sin, but is formed anew in pure hearts by grace. It follows rightly the beforementioned graces, because if they be not there, a clean heart is not created in a man.
By the pure are here meant those who possess a perfect goodness, conscious to themselves of no evil thoughts, or again those who live in such temperance as is mostly necessary to seeing God according to that of St. Paul, 'Follow peace with all men, and holiness, without which no man shall see God.' For as there are many merciful, yet unchaste, to shew that mercy alone is not enough, he adds this concerning purity.