The text of the Testament of Jacob here translated is the Coptic (Bohairic) text contained in Cod. Vat. Copt. 61. There are also versions extant in Arabic and Ethiopic. For particulars about these. versions, their interrelationship, and for some views on the relationship of the Testament of Jacob to the Testaments of Abraham and Isaac, reference should be made to the prefatory remarks on the Testament of Isaac (above, pp. 423-425).
To what is said there only one further observation need be added. The distinguishing marks of the Testament of Jacob, i.e. its essentially derivative character (especially its dependence on the book of Genesis) and the impression that the Christian elements in it are less easily detachable than in the Testament of Isaac, coupled with the fact that no Sahidic text of it has been preserved (as is the case with the Testament of Isaac), might suggest an origin independent of both the Testaments of Abraham and of Isaac. It might be argued, for example, that the Testament of Abraham was written first, in Greek: that the Testament of Isaac came later as an independent work (though whether written in Greek, or Sahidic, or anything else, it is impossible to say); and that later still the Bohairic translator of these two Testaments put them together and himself composed (in Bohairic) a Testament of Jacob to make a trilogy.
At the other extreme, though perhaps with less cogency, it might be argued that the three Testaments were designed as a trilogy from the start, and that all three, therefore, were originally written in Greek. In this case, it will be pure accident that only the Testament of Abraham has survived in Greek, that there are no surviving Sahidic texts of either it or the Testament of Jacob, and that the Bohairic is the first extant text to group all three together.