Just look again at Clement's statement in Stromata Book Five where the original point of his argument is that Jesus and Paul taught the commandment 'thou shalt not be angry' as well as 'thou shalt not lust':
For he (Pythagoras) intimated that it was necessary not only to efface the mark, but not to leave even a trace of anger; and that on its ceasing to boil, it was to be composed, and all memory of injury to be wiped out. "And let the sun upon your wrath (ἥλιος δὲ ὑμῖν τῇ ὀργῇ,)," says the Scripture, "go down (μὴ ἐπιδυέτω)." And he that said, "Thou shall not lust (οὐκ ἐπιθυμήσεις)," took away all memory of wrong; for wrath (θυμὸς) is found to be the impulse of lust (ἐπιθυμίας) in a mild soul, especially seeking irrational revenge. In the same way "the bed is ordered to be shaken up," (= a saying of Pythagoras) so that there may be no recollection of effusion in sleep, or sleep in the day-time; nor, besides, of pleasure during the night. And he intimated that the vision of the dark ought to be dissipated speedily by the light of truth. "Be angry, and sin not (ὀργίζεσθε καὶ μὴ ἁμαρτάνετε)," says David, teaching us that we ought not to assent to the impression, and not to follow it up by action, and so confirm wrath (τὴν ὀργὴν χρῆναι διδάσκων). [Strom 5.5.28]
The passage is clearly corrupt. We have been noting for some time that there is evidence that Eusebius or some other later redactor systematically went through Clement's references to the Pauline material and 'straightened' them so as to not make them look heretical.
In this particular case Clement - absurdly - uses Psalm 4:4 LXX following the Catholic text of Ephesians. Yet the saying contradicts the very point he is trying to make. In other words, it is plainly apparent that what Clement was actually trying to say was 'do not be angry' and Psalm 4:4 says 'be angry' and 'you do not sin.' Indeed Psalm 4:4 in Hebrew actually says 'do not tremble' or 'do not get excited' but the point here is that Clement plainly means to say 'do not be angry' (οὐκ ὀργίζεσθε). He probably wrote it originally. It was undoubtedly there in the Apostolikon that he shared with the Marcionites and other heretics just as Romans 7:7 confirmed the other part of the saying - 'do not lust' (οὐκ ἐπιθυμήσεις) - but here we have another clear example of subsequent Catholic 'correction' of the Pauline letters, and perhaps more significantly, the writings of Clement as well.