Jesus heard the blind man's cry as He was passing, by His Humanity He pitied him, and the power of His Divinity has driven away the darkness from our mind; setting in order all changeable things. But the Lord calls the blind man, who cries to Him, just like how He sends the word of faith to the people of the Gentiles through preachers; and they call on the blind man to be of good cheer and to rise, and bid him come to the Lord, when by preaching to the simple, they bid him have hope of salvation, and rise from the sloth of vice, and gird themselves for a life of virtue. Again, he throws away his garment and heaps, who, throwing aside the bonds of the world, with unencumbered pace hastens to the Giver of eternal light.
Therefore let us also imitate Bartimaeus, let us not seek for riches, earthly goods, or honors from the Lord, but for that Light, which we alone with the Angels can see, the way to which is faith; wherefore also Christ answers to the blind man, "Your faith has saved you". But he sees and follows who works what his understanding tells him is good; for he follows Jesus, who understands and executes what is good, who imitates Him, who had no wish to prosper in this world, and bore reproach and derision. And because we have fallen from inward joy, by delight in the things of the body, Jesus shows us what bitter feelings the return to God will cost us.
"Lord Jesus Christ, Son of God, have mercy on me" is known as the "Jesus Prayer". It is used by the Eastern Churches to achieve the goal of unceasing prayer as explained in the Russian spiritual classic: "The Way of a Pilgrim". Do not underestimate the power of simple prayers, for both the Publican and the Prodigal Son were reconciled to God by a single phrase.
On the Gospel of Mark (St. Bede the Venerable)