The term behind those who are taught
could also be translated as the learned,
or disciples
(see also Isaiah 8:16; Isaiah 54:13). This is an expert tongue of a disciple, suited to declare effectively the message learned from by his master. This is the prophetic duty of the Servant, who, having intimate association with the Lord, can speak with understanding as the disciple par excellence, in contrast to the children of Zion who lacked understanding.1 This confirms what was said in Isaiah 49:2, that the Servant’s task is a prophetic one, wherein he is to bring God’s word to the world.2
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.