The limitless loving devotion to God, and the gift God makes of Himself to you, are the highest elevation of which the heart is capable; it is the highest degree of prayer. The souls that have reached this point are truly the heart of the Church.
Meaning of the quote
The deepest love and closeness we can have with God is the highest level of prayer. When we feel God's great love for us and fully give ourselves to Him, it reaches the highest point our hearts can feel. The people who have experienced this special connection with God are the most important part of the Church.

About Edith Stein
Edith Stein was a German Jewish philosopher who converted to Catholicism and became a Carmelite nun. She was murdered in the Auschwitz gas chambers during the Holocaust. Edith Stein is now a canonized saint and one of the patron saints of Europe.
More quotes from Edith Stein
One could say that in case of need, every normal and healthy woman is able to hold a position. And there is no profession which cannot be practiced by a woman.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
As for what concerns our relations with our fellow men, the anguish in our neighbor’s soul must break all precept. All that we do is a means to an end, but love is an end in itself, because God is love.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
The nation… doesn’t simply need what we have. It needs what we are.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
On the question of relating to our fellowman – our neighbor’s spiritual need transcends every commandment. Everything else we do is a means to an end. But love is an end already, since God is love.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
The limitless loving devotion to God, and the gift God makes of Himself to you, are the highest elevation of which the heart is capable; it is the highest degree of prayer. The souls that have reached this point are truly the heart of the Church.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
Those who join the Carmelite Order are not lost to their near and dear ones, but have been won for them, because it is our vocation to intercede to God for everyone.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
In order to be an image of God, the spirit must turn to what is eternal, hold it in spirit, keep it in memory, and by loving it, embrace it in the will.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
My longing for truth was a single prayer.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
If anyone comes to me, I want to lead them to Him.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)
Every true prayer is a prayer of the Church; by means of that prayer the Church prays, since it is the Holy Spirit living in the Church, Who in every single soul ‘prays in us with unspeakable groanings’.
Jewish-German Catholic nun, theologian and philosopher (1891-1942)