“Blessed are the pure in heart, for they shall see God.” (Matthew 5:8) Purity of heart means to be free of all wicked motivations and sinful intentions, and to have no unworthy interests and self-seeking desires. It means to be totally free from anything which blinds and darkens the mind so that it cannot see things clearly and honestly. It means to be totally liberated from anything which captivates and darkens the soul so that it cannot reflect and shine with the pure light of God.
In another place in His Sermon on the Mount, the Lord has said.
The eye is the lamp of the body. So if your eye is sound, your body will be full of light; but if your eye is not sound, your whole body will be full of darkness. If then the light that is in you is darkness, how great is that darkness! (Matthew 7:22-23)
The pure in heart are those whose eyes are sound. The pure in heart are those who can say with the psalmist:
The Lord is my light and my salvation; whom shall I fear?
The Lord is the strength of my life; of whom shall I be afraid?
One thing have I asked of the Lord, that will I seek after;
that I may dwell in the house of the Lord all the days of my life.
Thou hast said, “Seek ye my face!” My heart says to Thee,
“Thy face, O Lord, do I seek.”
Hide not Thy face from me. (Psalm 27)
To seek but one thing, the face of the Lord, is purity of heart. To will but one thing, the light of the Lord in the depth of one’s soul, is to live in utter purity. It is for this reason that Christ’s mother Mary is the image of perfect purity. The holy Virgin is “all-pure” not merely because of her bodily continence, but also because of her spiritual soundness. Her heart was pure. Her mind was sane. Her soul magnified the Lord. Her spirit rejoiced in God her Savior. Her body was His spiritual temple. For this reason God regarded her humility and did great things for her. For this reason all generations call her blessed. For this reason she is “full of grace” and the Lord is with her. For she, in her simple purity could say to God: “Let it be to me according to Your word.” (Cf. Luke 1)
In the spiritual tradition of the Orthodox Church, purity of heart is an essential condition for union with God. When man’s heart is purified from all evil, it naturally shines with the light of God since God dwells in the soul. This is the doctrine of the saints as expressed by Saint Gregory of Nyssa.
… the man who purifies the eye of his soul will enjoy an immediate vision of God… it is the same lesson taught by the Word (i.e. Christ) when He said, “The Kingdom of God is within you.” (Luke 17:21) This teaches us that the man who purifies his heart of every passionate impulse will see the image of the divine nature in his own beauty.
You must then wash away, by a life of virtue, the dirt which has clung to your heart like plaster, and then your divine beauty will once again shine forth. (On the Beatitudes, Sermon 6)
The Apostle Paul has said the same thing in his pastoral letters.
To the pure all things are pure, but to the corrupt and faithless nothing is pure; their minds and con- sciences are corrupted. They profess to know God, but they deny Him by their deeds; they are detest- able, disobedient, unfit for any good deed. (Titus 1:15-16)
If anyone purifies himself from what is ignoble, then he will be a vessel of noble use, consecrated and useful to the master… ready for any good work. So shun youthful passions and aim at righteousness, faith, love and peace, along with those who call upon the Lord from a pure heart. (2 Timothy 2:21-22)
