There are in total four Servant songs: Isaiah 42:1–4; Isaiah 49:1–6; Isaiah 50:4–9; Isaiah 52:13–53:12. This third song develops the suffering and endurance of the Servant, matters only hinted at in the previous songs. This all serves to prepare for the fourth song, where the Servant’s suffering and his vindication are treated with equal emphasis.1
4 The Lord GOD has given me the tongue of those who are taught, that I may know how to sustain with a word him who is weary. Morning by morning he awakens; he awakens my ear to hear as those who are taught.