Stephen De Young (Eastern Orthodox) discusses the prophecy in Testament of Benjamin 3 that calls the Messiah the "Lamb of God"; argues it fits the Second Temple interpretation of Isaiah 53.
Stephen De Young, Apocrypha: An Introduction to Extra-Biblical Literature (Chesterton, IN: Ancient Faith Publishing, 2023), 155-56
Prophecy of the Messiah
The Testament of Benjamin includes one final prophecy of the coming Messiah, though it differs somewhat between the Aramaic and the Greek. In this prophecy also, the Greek includes additional details, but the broad strokes in both are the same. The shorter Aramaic form describes the coming of the Messiah as the point at which the spotless one will be seized by lawless men, and the sinless one will die for the impious men. The Greek version fleshes this out by referring to the Messiah as the Lamb of God, the Savior of the world, and adding that the Messiah will use the blood of the covenant to save the Gentiles and Israel, and to defeat Belial and his servants.
Typically, scholars see the Greek expansion as a later Christian interpolation. This is certainly possible, though the Testaments of the Twelve Patriarchs elsewhere mirror the language used here. The expansion could, therefore, simply be a means of summarizing the messianic material of the whole work here at its end. In theory, either a Christian or a Jewish author could have constructed such a summary. Here the suffering and death of the Messiah—the major interpretive understanding of the latter portions of Isaiah in the Second Temple period—is not specifically joined, for example, to the Cross or the Resurrection. These would have been tantalizing additions if a Christian intended to make these prophecies appear more specific.