Justin Martyr, First Apology 66
We call this food the Eucharist, and no one may share in it except the person who believes that what we teach is true, who has been washed in the bath for the forgiveness of sins and for rebirth, and who lives as Christ handed down.
For we do not receive these as common bread or common drink. Rather, just as Jesus Christ our Savior was made flesh through the word of God and took on flesh and blood for our salvation, so we have been taught that the food sanctified by the word of prayer — the food from which our flesh and blood are nourished through transformation — is the flesh and blood of that Jesus who was made flesh.
The apostles, in the memoirs they composed — which are called Gospels — handed down that Jesus took bread, gave thanks, and said, "Do this in remembrance of me; this is my body" (Luke 22:19-20). In the same way he took the cup, gave thanks, and said, "This is my blood" (Luke 22:19-20), and he gave it to them alone.
The evil demons imitated this and handed it down to be done in the mysteries of Mithras. For in the rites of the one being initiated, bread and a cup of water are placed with certain words spoken over them, as you know or are able to learn.
Greek
Καὶ ἡ τροφὴ αὕτη καλεῖται παρ᾿ ἡ μῖν εὐχαριστία, ἧς οὐδενὶ ἄλλῳ μετασχεῖν ἐξόν ἐστιν ἢ τῷ πιστεύοντι ἀληθῆ εἶναι τὰ δεδιδαγμένα ὑφ᾿ ἡμῶν, καὶ λουσαμένῳ τὸ ὑπὲρ ἀφέσεως ἁμαρτιῶν καὶ εἰς ἀναγέννησιν λουτρόν, καὶ οὕτως βιοῦντι ὡς ὁ Χριστὸς παρέδωκεν. Οὐ γὰρ ὡς κοινὸν ἄρτον οὐδὲ κοινὸν πόμα ταῦτα λαμβάνομεν· ἀλλ᾿ ὃν τρόπον διὰ λόγου θεοῦ σαρκοποιηθεὶς Ἰησοῦς Χριστὸς ὁ σωτὴρ ἡμῶν καὶ σάρκα καὶ αἷμα ὑπὲρ σωτηρίας ἡμῶν ἔσχεν, οὕτως καὶ τὴν δι᾿ εὐχῆς λόγου τοῦ παρ᾿ αὐτοῦ εὐχαριστηθεῖσαν τροφήν, ἐξ ἠς αἷμα καὶ σάρκες κατὰ μεταβολὴν τρέφονται ἡμῶν, ἐκείνου τοῦ σαρκοποιηθέντος Ἰησοῦ καὶ σάρκα καὶ αἷμα ἐδιδάχθημεν εἶναι. Οἱ γὰρ ἀπόστολοι ἐν τοῖς γενομένοις ὑπ᾿ αὐτῶν ἀπομνημονεύμασιν, ἃ καλεῖται εὐαγγέλια, οὕτως παρέδωκαν ἐντετάλθαι αὐτοῖς, τὸν Ἰησοῦν λαβόντα ἄρτον εὐχαριστήσαντα εἰπεῖν· „Τοῦτο ποιεῖτε εἰς τὴν ἀνάμνησίν μου, τοῦτό ἐστι τὸ σῶμά μου“· καὶ τὸ ποτήριον ὁμοίως λαβόντα καὶ εὐχαριστήσαντα εἰπεῖν· Τοῦτό ἐστι τὸ αἷμά μου“· καὶ μόνοις αὐτοῖς μεταδοῦναι. Ὅπερ καὶ ἐν τοῖς τοῖ Μίθρα μυστηρίοις παρέδωκαν γίνεσθαι μιμησάμενοι οἱ πονηροὶ δαίμονες· ὅτι γὰρ ἄρτος καὶ ποτήριον ὕδατος τίθεται ἐν ταῖς τοῦ μυουμένου τελεταῖς μετ᾿ ἐπιλόγων τινῶν, ἢ ἐπίστασθε ἢ μαθεῖν δύνασθε.