"I [Justin] continued, to contend against you about the reading which you so interpret, saying it is written, 'Till the things laid up for Him come;' though the Seventy have not so explained it, but thus, 'Till He comes for whom this is laid up.' But since what follows indicates that the reference is to Christ (for it is,'and He shall be the expectation of nations'), I do not proceed to have a mere verbal controversy with you, as I have not attempted to establish proof about Christ from the passages of Scripture which are not admitted by you which I quoted from the words of Jeremiah the prophet, and Esdras, and David; but from those which are even now admitted by you, which had your teachers comprehended, be well assured they would have deleted them, as they did those about the death of Isaiah, whom you sawed asunder with a wooden saw" (Dial. CXX).
"But in the version of the Seventy it is written, 'Behold, ye die like men, and fall like one of the princes,' in order to manifest the disobedience of men,-I mean of Adam and Eve,-and the fall of one of the princes, i.e., of him who was called the serpent,
who fell with a great overthrow, because he deceived Eve" (Dial. CXXIV).
Also, in Dial. LXXIII, Justin quotes Ps. 96:10 [95:10 LXX] as it evidently appeared in some copies of the LXX concerning the Lord reigning from a tree (Ειπατε εν τοις εθνεσι, ὁ Κυριος εβασιλευσε απο του ξυλου). He apparently had to get this reading from some version of the LXX although he may be the only Greek writer to quote the psalm in this way (a number of Latin writers cite the psalm as the Martyr does).
Robert Kraft offers these insights:
We have already noted (above, p. 209) that Justin thought Jews had excised the words [apo tou xylou] from Ps.95/96.10. Numerous preserved MSS and versions (especially "western" and south Egyptian) also support this reading, which Justin viewed as Pre-Christian, prophetic and original\31). It is not, however, found in the extant Hebrew text or in the well attested northern Egyptian Greek text. Its origin remains a mystery. If it is a Christian addition, it predates Justin (and probably Barnabas, as well -- see Barn. 8.5) and thus developed in the first century of Christian existence.