There is a long tradition in the Eastern Orthodox Chuch, stretching back to the Desert Fathers, of the continuous internal recitation of the Jesus Prayer, based on Paul’s counsel to “pray without ceasing” in his First Epistle to the Thessalonians.
There are many variations of the Jesus prayer but the most popular is this:
“Jesus Christ, Son of God, have mercy on me, a sinner.”
As the prayer is repeated, one can imagine his or her mind sinking from the head down into the heart.
If you recite this prayer continuously, as often as you can remember, during times set aside for prayer, as well as while you’re going about your daily activities, the prayer will eventually be recited continuously and silently by the heart until one is illuminated by the Holy Spirit, realizing theosis, or union with the Divine.
Below you’ll find a beautiful description of Christian contemplation, written by Thomas Merton, and voiced by Samaneri Jayasāra: