With this note about the Servant knowing how to sustain the weary with a word, he reflects what is previously said about the Servant: he brings a word with gentle speech (Isaiah 42:2), he has incisive speech like a sharpened sword (Isaiah 49:2) and he has a pure mouth (Isaiah 53:7, Isaiah 53:9).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.