Blessed are the pure in heart,.... Not in the head; for men may have pure notions and impure hearts; not in the hand, or action, or in outward conversation only; so the Pharisees were outwardly righteous before men, but inwardly full of impurity; but "in heart".
The heart of man is naturally unclean; nor is it in the power of man to make it clean, or to be pure from his sin; nor is any man in this life, in such sense, so pure in heart, as to be entirely free from sin.
This is only true of Christ, angels, and glorified saints: but such may be said to be so, who, though they have sin dwelling in them, are justified from all sin, by the righteousness of Christ, and are "clean through the word", or sentence of justification pronounced upon them, on the account of that righteousness; whose iniquities are all of them forgiven, and whose hearts are sprinkled with the blood of Jesus, which cleanses from all sin; and who have the grace of God wrought in their hearts, which, though as yet imperfect, it is entirely pure; there is not the least spot or stain of sin in it: and such souls as they are in love with, so they most earnestly desire after more purity of heart, lip, life, and conversation.