Blessed are the pure in heart.

From the Lord’s sermon on the mount

Create in me a clean heart, O God.

Psalm 50

Keep watch over your heart throughout your life. Keep an eye on, and pay attention to, what it is that impedes you from uniting it to all-blessed God.

St. John of Kronstadt

The essence and basic cause of salvation lies in keeping the heart from sinful thoughts.

St. Ignatius Brianchaninov

The heart is the organ of highest cognition, the means of communication with God and with the entire transcendental world.

St. Luke (Voino-Yasenetsky)