Still - not "every forged/interpolated/edited" document is so useful.
For example - -
The Didache
"But every Lord’s day . . . gather yourselves together and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure. But let no one that is at variance with his fellow come together with you, until they be reconciled, that your sacrifice may not be profaned" (Didache 14 [A.D. 70]).
The Letter of Barnabas
"We keep the eighth day [Sunday] with joyfulness, the day also on which Jesus rose again from the dead" (Letter of Barnabas 15:6–8 [A.D. 74]).
=========================================== regarding the fraudulent/forged letter
Neander
"The writings of the so-called Apostolic Fathers are, alas! come down to us, for the most part, in a very uncertain condition; partly, because in early times writings were counterfeited, under the name of these venerable men of the church, in order to propagate certain opinions or principles; partly, because those writings which they had really published were adulterated, and especially so to serve a Judao-hierarchical party, which would fain crush the free evangelical spirit. We should here, in the first place, have to name Bamabas, the well known fellow traveler of St. Paul, if a letter, which was first known in the second century, in the Alexandrian church, under his name, and which bore the inscription of a Catholic epistle, was really his composition.
But it is impossible that we should acknowledge this epistle to belong to that Barnabas who was worthy to be the companion of the apostolic labors of St. Paul, and had received his name from the power of his animated discourses in the churches. We find, also, nothing to induce us to believe the author of the Epistle was desirous of being considered Barnabas. But since its spirit and its mode of conception corresponded to the Alexandrian taste, it may have happened, that as the author's name was unknown, and persons were desirous of giving it authority, a report was spread abroad in Alexandria, that Barnabas was the author." (History of the Christian Church of the First Three Centuries, pp. 407, 408, Rose's Trans.)
Mosheim says:
"The Epistle of Barnabas was the production of some Jew, who most probably lived in this [the second] century, and whose mean abilities and superstitious attachment to Jewish fables, show, notwithstanding the uprightness of his intentions, that he must have been a very different person from the true Barnabas who was St. Paul's companion." (Church History, Vol. 1, p. 113, Maclaine's Trans.)
Also from the same author:
"For what is suggested by some of its having been written by that Barnabas who was the friend and companion of St. Paul, the futility of such a notion is easily to be made apparent from the letter itself. Several of the opinions and interpretations of Scripture which it contains, having in them so little, either of truth, or dignity, or force, as to render it impossible that they ever could have proceeded from the pen of a man divinely inspired." (Historical Commentaries, Century 2, See. 53.)
Eusebius says:
"Among the rejected writings must be reckoned also the Acts of Paul, and the so-called Shepherd, and the Apocalypse of Peter, and in addition to these the extant Epistle of Barnabas, and the so-called Teachings of the Apostles." (Church History, Book III., chap. 25, Sec. 4. The Nicene and Post-Nicene Fathers, Vol. I., p. 156.
Prof. Hackett says:
"The letter still extant, which was known as that of Bamabas, even in the second century, cannot be defended as genuine. (Commentary on Acts, p. 251.)
Millner says:
"Of the Apostle Barnabas, nothing is known, except what is recorded in the Acts. There we have an honorable enconium of his character, and a particular description of his joint labors with St. Paul. It is a great injury to him, to apprehend the Epistle which goes by his name to be his." (Vol. I., p. 126, Church History. Boston, 1809.)
Kitto says:
"The so-called Epistle of Barnabas, probably a forgery of the second century." (Cyclopedia Biblical Literature, article Lord's-day.)
Sir William Domville, after an exhaustive examination of the whole question, concludes as follows:
"But the Epistle was not written by Bamabas; it is not merely "unworthy of him," it would be a disgrace to him, and, what is of much more consequence, it would be a disgrace to the Christian religion, as being the production of one of the authorized teachers of that religion in the time of the apostles, which circumstance would seriously damage the evidence of its divine origin." (An Examination of the Six Texts, p. 233.)
Prof. W.D. Killen, a prominent representative of the Presbyterian church in Ireland, bears testimony as follows:
"The tract known as the "Epistle of Barnabas" was probably composed in A.D. 135. It is the production, apparently, of a convert from Judaism, who took special pleasure in allegorical interpretation of Scripture." (History of the Ancient Church, p. 367. New York, 1859. See also The Old Catholic Church, pp. 8, 13. T. & T. Clark, 1871.)
Rev. Lyman Coleman says:
"The Epistle of Barnabas, bearing the honored name of the companion of Paul in his missionary labors, is evidently spurious. It abounds in fabulous narratives, mystic allegorical interpretations of the Old Testament, and fanciful conceits; and is generally agreed by the learned to be of no authority. Neander supposes it to have originated in the Alexandrian school; but at what particular time he does not define. (Ancient Christianity Exemplified. chap. 2, sec. 2, p. 47. Philadelphia, 1852.)
Dr. Schaff rejects the theory that the Epistle is genuine, and says:
"The author was probably a converted Jew from Alexandria (perhaps by the name Barnabas, which would easily explain the confusion), to judge from his familiarity with Jewish literature, and, apparently, with Philo, and his allegorical method in handling the Old Testament. In Egypt his Epistle was first known and most esteemed, and the Sinaitic Bible which contains it was probably written in Alexandria or Caesarea in Palestine. The readers were chiefly Jewish Christians in Egypt, and the East, who overestimated the Mosaic traditions and ceremonies." (History Christian Church, Vol. II., p. 677. New York, 1883.)