This saying is quoted three times in the Clementine Homilies as spoken by our Lord.  See Hom. II. § 51; III. § 50; XVIII. § 20:  “Every man who wishes to be saved must become, as the Teacher said, a judge of the books written to try us.  For thus He spake:  Become experienced bankers.  Now the need of bankers arises from the circumstance that the spurious is mixed up with the genuine.” On the same saying, quoted as Scripture in the Apostolic Constitutions (II. § 36), Cotelerius suggests that in oral tradition, or in some Apocryphal book, the proverb was said to come from the Old Testament, and was added by some transcriber as a gloss in the margin of Matt. xxv. 27, or Luke xix. 23.  Dionysius of Alexandria, Epist. VII., speaks of “the Apostolic word, which thus urges all who are endowed with greater virtue, ‘Be ye skillful money-changers,’” referring apparently as here to 1 Thess. v. 21, 22, “try all things, &c.”  (See Euseb. E.H. VII. ch. 6 in this series:  Suicer. Thesaurus, Τραπεζίτης:  and Resch. (Agrapha, pp. 233–239.)