This is a reflection of the trinity: Kether (the Father), Chokmah (the Son), and Binah (the Holy Spirit), which are not three separate entities, but one force expressed in three attributes. Our psycho-physiology mirrors the Christ, with Kether in the intellectual brain, Chokmah in the emotional brain, and Binah in the motor-instinctive-sexual brain. The Christ manages the energies of our three brains, therefore when we pray, we often invoke the Logoic Trinity three times so as to be in harmony with the three aspects of our Internal God, through mustering all of our thought, feeling and will in submission to the Lord. While this is effective, it is not mandatory in order to pray.
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"