In the next place, Celsus forgets that he is addressing Christians, who pray to God alone through Jesus; and mixing up other notions with theirs, he absurdly attributes them all to Christians. “If,” says he, “they who are addressed are called upon by barbarous names, they will have power, but no longer will they have any if they are addressed in Greek or Latin.” Let him, then, state plainly whom we call upon for help by barbarous names. Any one will be convinced that this is a false charge which Celsus brings against us, when he considers that Christians in prayer do not even use the precise names which divine Scripture applies to God; but the Greeks use Greek names, the Romans Latin names, and every one prays and sings praises to God as he best can, in his mother tongue. For the Lord of all the languages of the earth hears those who pray to Him in each different tongue, hearing, if I may so say, but one voice, expressing itself in different dialects. For the Most High is not as one of those who select one language, Barbarian or Greek, knowing nothing of any other, and caring nothing for those who speak in other tongues.
Source: Against Celsus (New Advent)