If Justin's text differs from the received text of the LXX, it is frequently found that he has some extant authority for his reading.

The way in which Credner has drawn out these varieties of reading, and the results which he obtained as to the relations and comparative value of the different MSS., form perhaps the most interesting feature of his work.

The more marked divergences in Justin may be referred to two causes; (1) quotation from memory, in which he indulges freely, especially in the shorter passages, and more in the Apology than in the Dialogue with Tryphon; (2) in Messianic passages the use of a Targum, not immediately by Justin himself but in some previous document from which he quotes, in order to introduce a more distinctly Christian interpretation; the coincidences between Justin and other Christian writers show that the text of the LXX had been thus modified in a Christian sense, generally through a closer comparison with and nearer return to the Hebrew, before his time.
The instances of free quotation are not perhaps quite fully given in the above list, but it will be seen that though they form a marked phenomenon, still more marked is the amount of exactness.
Any long, not Messianic, passage, it appears to be the rule with Justin to quote exactly.

Among the passages quoted freely there seem to be none of greater length than four verses.
The exactness is especially remarkable in the plain historical narratives of the Pentateuch and the Psalms, though it is also evident that Justin had the MS.

before him, and referred to it frequently throughout the quotations from the latter part of Isaiah.