In its dialogue with Tryphon, Justin refers to many Jewish exegesions, beliefs and practices explicitly presented as contemporary. The generally accepted assumption that he would have derived this information from one or more previous writing (s) does not stand up to scrutiny: a comparison with various old sources — Judeo-Greek literature, intertestamentary writing and quarry writing, New Testament and Christian literature of the first centuries — highlights Justin’s specificity in this area. On the other hand, reconciliations with rabbinic literature show that what Justin reports is almost always attributed in Talmud and Midrash to Palestinian rabbits of the second and third centuries. There is therefore every reason to believe that the apologist’s information is first-hand.