Clement quotes Clement of Rome as an Apostle

Moreover, in the Epistle to the Corinthians, the Apostle Clement also, drawing a picture of the Gnostic, says: “For who that has sojourned among you has not proved your perfect and firm faith? and has not admired your sound and gentle piety? and has not celebrated the munificent style of your hospitality? and has not felicitated your complete and sure knowledge? For ye did all things impartially, and walked in the ordinances of God;” and so forth.

Clement of Alexandria
The Stromata, Book IV
Chapter XVII

The Gospel of Matthew was written to the Jews

The Gospel according to Matthew was written to the Jews. For they laid particular stress upon the fact that Christ [should be] of the seed of David. Matthew also, who had a still greater desire [to establish this point], took particular pains to afford them convincing proof that Christ is of the seed of David; and therefore he commences with [an account of] His genealogy.

Irenaeus of Lyons
Lost Writings
Fragment XXIX

The number of the beast: 666, not 616

I do not know how it is that some have erred following the ordinary mode of speech, and have vitiated the middle number in the name, deducting the amount of fifty from it, so that instead of six decads they will have it that there is but one. [I am inclined to think that this occurred through the fault of the copyists, as is wont to happen, since numbers also are expressed by letters; so that the Greek letter which expresses the number sixty was easily expanded into the letter Iota of the Greeks.]

But, knowing the sure number declared by Scripture, that is, six hundred sixty and six…

Irenaeus of Lyons
Against Heresies, Book V
Chapter XXX