The Servant Songs is a name applied to four passages in Deutero-Isaiah (Isa 42:1-4; 49:1-6; 50:4-11; 52:13-53:12). Bernhard Duhm in his watershed commentary on Isaiah isolated these servant songs as a distinct from Deutero-Isaiah, and argued that they were added at a later time. Most scholars today do not follow Duhm’s hypothesis, but it has exerted enormous influence. Through the songs we learn that the servant can be described as a ‘messianic’ figure, one chosen by Yahweh before birth, endowed with the Spirit of Yahweh, his mission is not limited to Israel, and one who suffers physical violence as substitute for sin. Much of the discussion revolves around the identification of the servant. The descriptions mirror those of prophets, like Jeremiah, as well as other descriptions of future David kings (i.e. Zerbbabel). There is no consensus on the figure. The issue is made more complex since the songs are not internally consistent about this fact themselves. For example, in the second song, 49:3 explicitly states “You are my servant O Israel” whereas two verses later it states his mission is to “turn back Jacob to him” (49:5).
Coogan, the Old Testament: A Historical and Literary Introduction to the Hebrew Scriptures