The habits of the Fathers in quotation were very loose. Having no concordances or indices, or anything resembling the modern apparatus for facilitating reference, and often no manuscript, they were frequently compelled to rely upon memory for their citations. Quoting from memory explains what we so often find, combinations of different passages, transpositions, and sense-renderings. Though a full summary of the whole gospel life could be composed from the quotations of Justin Martyr, his quotations are careless. He quotes the same passage differently on different occasions. Although he cites written documents, he often quotes from memory, and interweaves words which are given separately by the Synoptists. He condenses, combines, and transposes the language of the Lord as recorded in the Gospel records. Take, for example. Matt. 5:22, 39, 40, 41, and Luke 6:29. In Justin, 1 Apol. XVI, we read τῷ τυπτόντι σοῦ τὴν σιαγόνα πάρεχε καὶ τὴν ἄλλην, καὶ τὸν αἴροντα σοῦ τὸν χιτῶνα ἢ τὸ ἱμάτον μὴ κωλύσῃς. ̔́Ος δὲ ἂν ὀργισθῇ ἐνοχός ἐστιν εἰς τὸ πῦρ, παντὶ δὲ ἀγγαρεύοντί σε μίλιον ἀκολούθησον. Here we have several verses massed, apparently from two Evangelists. Luke is literally followed in the first nine words. The order of the Gospel is not observed, and the sense is changed in the words about the coat and the cloke.
Similarly Matt. 5:46 ; comp. Luke 6:27. Justin, 1 Apol. XV: εἰ ἀγαπᾶτε τοὺς ἀγαπῶντας ὑμᾶς, τί καινὸν ποιεῖτε; καὶ γὰρ οἱ πόρνοι τοῦτο ποιοῦσιν. Here, instead of "What reward have ye?" Justin has "What new thing do ye do?" For "publicans" he gives "fornicators."
Again, see Clement of Alexandria, Strom. III, 4, 36, where Matt. 5:16 is given τὰ ἀγαθὰ ὑμιν ἔργα λαμψάτω, "Let your good works shine."
The Apostolic Fathers are of little value for patristic quotation, since they do not so much quote as blend the language of the New Testament with their own. Fragments of most of the canonical Epistles are embedded in their writings, and their diction is more or less coloured by that of the apostolic books and different passages are combined.