In the Hebrew tradition, to do a thing in the name of another, or to invoke and call upon his name, are acts of weight and potency. To invoke a person's name is to make that person effectively present. One makes a name alive by mentioning it. The name immediately calls forth the soul it designated; therefore there is such deep significance in the very mention of a name.
Everything that is true of human names is true to an incomparably higher degree of the divine Name. The power and glory of God are present and active in his Name. The Name of God is numen praesens, God with us, Emmanuel. Attentively and deliberately to invoke God's name is to place oneself in his presence, to open oneself to his energy, to offer oneself as an instrument and a living sacrifice in his hands...
This Hebraic understanding of the Name passes for the Old Testament into the New. Devils are cast out and men are healed through the Name of Jesus., for the Name is power. Once this potency of the Name is properly appreciated, many familiar passages acquire a fuller meaning and force...
It is this biblical reverence for the Name that forms the basis and foundation of the Jesus Prayer. God's name is intimately linked with his Person, and so the invocation of the divine Name possesses a sacramental character, serving as an efficacious sign of his invisible presence and action. For the believing Christian roday, as in apostolic times, the Name of Jesus is power...
Kallistos Ware, The Power of the Name: The Jesus Prayer in Orthodox Spirituality
Now Thomas (also known as Didymus ), one of the Twelve, was not with the disciples when Jesus came. So the other disciples told him, "We have seen the Lord!" But he said to them, "Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe." A week later his disciples were in the house again, and Thomas was with them. Though the doors were locked, Jesus came and stood among them and said, "Peace be with you!" Then he said to Thomas, "Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe." Thomas said to him, "My Lord and my God!"
John 20:24-28I have come to realise, over the 40-odd years I have (more or less faithfully) prayed the Jesus Prayer, that these words are no more than a simple statement of fact. As long as the prayer is with me - and it does after a time become part of one's breathing, one's walking, one's dreaming even - then one is in the presence of God, and all one's actions, good and bad - and they will not all be good, believe me - will somehow be drawn together in God, so that, as it says in Proverbs 20.24, "All our steps are ordered by the Lord; how then can we understand our own ways?" It doesn't seem necessary to understand; all that does seem necessary, these days, is to pray, truly.
Lord Jesus Christ, Son of God, have mercy on me, a sinner...