The prayer you quote looks familiar. It may be from the third antiphone of the Divine Liturgy of +Basil the Great, the predecessor to the Divine Liturgy of +John Chrysostomos:
“O Thou who hast bestowed on us these common and accordant prayers, and dost promise that when two or three are gathered together in Thy name, Thou wilt grant their requests, fulfill even now the requests of thy servants as is expedient for them, granting us in this present age the knowledge of Thy truth, and in that to come, life eternal.”
Its sad the Fathers are so unknown among Protestants and that many in the Roman Church, and in Orthodoxy for that matter, don’t appreciate the great treasure we have in the writings and lives of The Fathers.
Benedict XVI is certainly doing his part to change that. As you are well aware, he has been teaching about the Early Church Fathers and their writings in his weekly audiences. He has a way of bringing them alive. I have learned much from his catecheses and they have only barely scratched the surface.