When you read in Scripture, the Kingdom of God is within us (Lk 17:21), what does this mean to you? The Church Fathers refer to this place within also as the "Heart." It is in this place that God has fashioned that God abides so He can manifest Himself through each person. The role of the Church is to help us discover this deep place of the "Heart" that is also the center of our soul.
It is the place within where we wage a battle for our salvation. This is the target of all our ascetic efforts. We want it to be made pure. Jesus has told us that the pure of Heart will see God. As we seek to become united with God, to overcome our sinfulness, we desire that our soul, its "Heart" be ignited by His grace.
Jesus told us, You shall love the Lord your God will all your heart, and with all your soul, and with all your mind, and with all your strength. (Matt 12:30) So, what does this mean? Saint Gregory Palamas says the heart is the body of our body, a place where our whole being becomes like a knot. When our mind and heart are united we have only one thought––the thought of God. All of our desire is focused on God. When we give our whole mind, our whole heart to God we are totally focused on Him. In this stance we receive His grace and are given the ability to do His will. In this way we attain what Apostle Paul meant when he said that Christ is formed in us (Gal 4:19). We become whole and are perfected.
We can never wholly contain God in our heart as He is infinite, something greater than our heart. He makes it a dwelling place, a temple of His divinity reflecting His image in us. When our whole heart and mind are turned to God we become holy, enlightened, "the light of the world." It is in this way that God directs our life, fulfilling the purpose He has for us.
Reflect on the following passage from the Sermon on the Mount where Jesus told His disciple the following:
You are the light of the world. A city set on a hill cannot be hidden. Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. In this same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven. (Matthew 5:14-16)We want to purify our heart so that is shines, becomes a great light, enabling us to take action in the world in a way that glorifies God, that encourages others to purify their hearts and to seek God with their whole heart and mind and soul. In this way the whole world can become a great light.
What is it that keeps us from becoming this light that Jesus speaks about? Our reality is that we are not able to give our whole heart and mind to God but instead are distracted by our passions, our earthly desires. We are not living with a focus on the "Heart" but on the things of this created world siphoning our attention away from God. Because of our fallen nature we have within us also the tendency to sin. As Paul says, "all have sinned and come short of the Glory of God." (Rom 3:23)
How are we to proceed? We must do as the prodigal son, recognize our condition and seek to return to our father's house which is within. We must uproot our sinful tendencies so that God's commandments will become alive in our heart instead of our passions and worldly desires.
This is a path of return that is difficult. There is only one way and that is to master our situation with God's help so we can follow the divine commandments. Archimandrite Zacharias writes,
There is no greater misfortune than that of an insensible and verified heart that is unable to distinguish between the luminous Way of God's Providence and the gloomy confusion of the ways of the world."Difficult, yes, but we know it is possible. We have an all powerful ally, God. His aim is for our "Heart" to become His temple. He says to us, "Behold, I stand at the door and knock: If anyone hears my voice, and opens the door, I will come to him, and will sup with him, and he with Me? (Rev 3"20). When we knock and the door is opened we discover the greatest of miracles. Our heart becomes united with the Holy Spirit. With an open "Heart" we can unify our mind with our heart and God will fill His Kingdom within us with His full goodness.
For this to happen God must first be able to converse with us. We must be capable of hearing Him and willing to surrender our will to His direction. In this way God can become the sole focus of our life. We must learn to develop an intimate relationship with Him so we can have an ongoing dialogue with Him
What gets in the way? It's our pride, our self-centeredness. We fail to see the larger picture and see our death as the end of everything that gives us pleasure. We become fearful and sinful seeking to satisfy our own needs. We are stuck until we can come to terms with the reality of our situation, just like the prodigal son before he was able to return to his father. We must say what the he said, "Father, I have sinned against heaven and before you and am no more worthy to be called your son. (Luke 15:19-19) In this way we are humbled. We discover how poorly we live by His commandments, how distant we are from Him. We see clearly our self-centeredness, our selfishness and pride. We become sorry for our condition and seek His help to return. From this realization we are motivated to make changes in our attitude and orientation toward life and God. We begin a long journey of purification where we liberate our "Heart" from all the bodily passions. In cooperation with Grace we will finally be able to surrender our whole being to Him, to commit our whole heart, our whole mind, and our whole soul to Him. We will discover the "Kingdom within."
Reference: The Hidden Man of the Heart by Archimandrite Zacharias