The Didache, Didache 12 (apostles / false prophets)
But let every apostle who comes to you be received as the Lord. Yet he shall not stay except one day; if there is need, also the next; but if he stays three days, he is a false prophet. And when the apostle goes out, let him take nothing except bread until he lodges; but if he asks for money, he is a false prophet.
Greek
πᾶς δὲ ἀπόστολος ἐρχόμενος πρὸς ὑμᾶς δεχθήτω ὡς κύριος· οὐ μενεῖ δὲ εἰ μὴ ἡμέραν μίαν· ἐὰν δὲ ᾖ χρεία, καὶ τὴν ἄλλην· τρεῖς δὲ ἐὰν μείνῃ, ψευδοπροφήτης ἐστίν. ἐξερχόμενος δὲ ὁ ἀπόστολος μηδὲν λαμβανέτω εἰ μὴ ἄρτον, ἕως οὗ αὐλισθῇ· ἐὰν δὲ ἀργύριον αἰτῇ, ψευδοπροφήτης ἐστί.