Fight neither against the brothers in Christ, nor against whatever nation, even a barbaric nation, if it made peace with you and wishes to keep it... I think all would call a fool someone who would believe that there is in the world a complete stranger. Because we are all children of One, even if we differ in language or whatever, even in faith. Well, human beings as we are, we need to care about people, and to wish for all any good, to help anyone, as is just and possible. Because our nature is common, and one earth for all, one roof, one light and one air is extended above all of us from the Creator. And in one word, what is His, is common to all of us. But you need also to understand what is more distant and less distant (because there exist many degrees in affinity) and to be good with all, as far as that depends on you, and to those who are closer to you, to offer yourself with due affinity and warmth in your relationship.

Precepts..., Patrologia Graeca 156.353-6 

Μηδὲ πολέμει πρὸς ἀδελφοὺς τοὺς ἀπὸ Χριστοῦ, μήτε μὴν πρὸς ὀντινοῦν, ἢ βαρβάρων ἔθνος, ἐν σπονδαῖς σοι καταστὰν καὶ τηρεῖν αὐτὰς ἐθέλον… Νομίζω πάντας ἂν φάναι ἠλίθιον ἄνθρωπον εἶναι τὸν νομίζοντα ἀλλότριον παντάπασιν ἄνθρωπον εἶναι. Πάντες γὰρ ἑνὸς ἔκγονα, κἂν διαλέκτῳ διαφερώμεθα, κἂν οἱστισινοῦν κἂν αὐτῷ σεβάσματι. Καὶ τοίνυν ἄνθρωπον ὄντα ἀνθρώπων κήδεσθαι δεῖ καὶ συνεύχεσθαι τοῖς ὅλοις ἀγαθά, ὡς ἐνόν, ὡς θέμις, ὡς ἔξεστι. Κοινὴ γὰρ ἡ φύσις καὶ πᾶσιν ἔδαφος ἓν καὶ ὀροφὴ μία καὶ ἕν τι φῶς καὶ εἷς ἀὴρ ἐφήπλωται παρὰ τοῦ δημιουργοῦ. Καὶ ἁπλῶς τὰ παρ' ἐκείνου κοινά. Χρὴ μέντοι διαστέλλειν τοῦ πορρωτέρω τὸ ἔγγιον (βαθμοὶ γὰρ πλεῖστοι τῆς οἰκειότητος) καὶ πᾶσι μὲν ἀγαθὸν εἶναι τὸ καθ' ἑαυτόν, τοῖς μᾶλλον δὲ ἐγγυτάτω ἀναλόγως γνησιώτερον προσφέρεσθαι. 

Cf. The Virtue of a King - Deacon Agapetus to Justinian (Romanian translation)

Byzantine History Resources / Byzantium: heir to the Graeco-roman antiquity / Greek Orthodoxy - From Apostolic Times to the Present Day

Cf. ARISTOPHANES : Unjust discourse, Puppet politics ||| PLATO : Totalitarianism is ignorance, Tyranny and slavery ||| CAVAFY : As much as you can ||| PAPATSONIS : Scheme, Hestia, Wisdom, In Rising Sound