Testament of Joseph speaks of the Messiah as a "spotless lamb."
Testament of Joseph 19 in H. C. Kee (trans.), "Testaments of the Twelve Patriarchs," The Old Testament Pseudepigrapha, ed. James H. Charlesworth, 2 vols. (New York: Yale University Press, 1983), 1: 824-25
1 “Listen, my children, concerning the dream that I saw. 2 Twelve stags were grazing at a certain place; nine were scattered over the whole earth, and likewise also the three.
8 And I saw that a virgin was born from Judah, wearing a linen stole; and from her was born a spotless lamb. At his left there was something like a lion, and all the wild animals rushed against him, but the lamb conquered them, and destroyed them, trampling them underfoot.
9 And the angels and mankind and all the earth rejoiced over him.
10 These things will take place in the last days.
11 You, therefore, my children, keep the Lord’s commandments; honor Levi and Judah, because from their seed will arise the Lamb of God who will take away the sin of the world, and will save all the nations, as well as Israel.
12 For his kingdom is an everlasting kingdom which will not pass away. But my kingdom will come to an end among you, like a guard in an orchard who disappears at the end of the summer.