St. Paul, 1 Corinthians
For though I be free from all men, yet have I made myself servant unto all, that I might gain the more.
And unto the Jews I became as a Jew, that I might gain the Jews; to them that are under the law, as under the law, that I might gain them that are under the law;
To them that are without law, as without law, (being not without law to God, but under the law to Christ,) that I might gain them that are without law.
To the weak became I as weak, that I might gain the weak: I am made all things to all men, that I might by all means save some.
ἐλεύθερος γὰρ ὢν ἐκ πάντων πᾶσιν ἐμαυτὸν ἐδούλωσα, ἵνα τοὺς πλείονας κερδήσω·
καὶ ἐγενόμην τοῖς Ἰουδαίοις ὡς Ἰουδαῖος, ἵνα Ἰουδαίους κερδήσω· τοῖς ὑπὸ νόμον ὡς ὑπὸ νόμον, μὴ ὢν αὐτὸς ὑπὸ νόμον, ἵνα τοὺς ὑπὸ νόμον κερδήσω·
τοῖς ἀνόμοις ὡς ἄνομος, μὴ ὢν ἄνομος θεοῦ ἀλλ’ ἔννομος Χριστοῦ, ἵνα κερδάνω τοὺς ἀνόμους·
ἐγενόμην τοῖς ἀσθενέσιν ἀσθενής, ἵνα τοὺς ἀσθενεῖς κερδήσω· τοῖς πᾶσιν γέγονα πάντα, ἵνα πάντως τινὰς σώσω.
Plutarch, Life of Alcibiades
23.5 (tr. Bernadotte Perrin):
In Sparta, he was all for bodily training, simplicity of life, and severity of countenance; in Ionia, for luxurious ease and pleasure; in Thrace, for drinking deep; in Thessaly, for riding hard; and when he was thrown with Tissaphernes the satrap, he outdid even Persian magnificence in his pomp and lavishness. It was not that he could so easily pass entirely from one manner of man to another, nor that he actually underwent in every case a change in his real character; but when he saw that his natural manners were likely to be annoying to his associates, he was quick to assume any counterfeit exterior which might in each case be suitable for them.
ἀλλ᾽ ἐν Σπάρτῃ γυμναστικός, εὐτελής, σκυθρωπός, ἐν Ἰωνίᾳ χλιδανός, ἐπιτερπής, ῥᾴθυμος, ἐν Θράκῃ μεθυστικός, ἐν Θετταλοῖς ἱππαστικός, Τισαφέρνῃ δὲ τῷ σατράπῃ συνὼν ὑπερέβαλεν ὄγκῳ καὶ πολυτελείᾳ τὴν Περσικὴν μεγαλοπρέπειαν, οὐχ αὑτὸν ἐξιστὰς οὕτω ῥᾳδίως εἰς ἕτερον ἐξ ἑτέρου τρόπον, οὐδὲ πᾶσαν δεχόμενος τῷ ἤθει μεταβολήν, ἀλλ᾽ ὅτι τῇ φύσει χρώμενος ἔμελλε λυπεῖν τοὺς ἐντυγχάνοντας, εἰς πᾶν ἀεὶ τὸ πρόσφορον ἐκείνοις σχῆμα καὶ πλάσμα κατεδύετο καὶ κατέφευγεν.
See Clarence E. Glad, Paul and Philodemus: Adaptability in Epicurean and Early Christian Psychagogy
(Leiden: Brill, 1995), pp. 29-30.