Isaiah 42:5-9 declares three things that “the Lord” will do to His people: “I have called you…I will take you…I will give you…”  This is a guarantee that His people will serve Him and carry out His purpose in the world.  Cf. Isaiah 42:6-7, especially the goal of being “a light for the nations…”  The theology for the Church is being conveyed through this description of God’s initiative, followed by the purpose or goal God has in mind.  If Isaiah 42 is relevant at all it’s because of a sequence like this: God’s people fail to function as His servants, God’s Servant succeeds (through His perfect life, substitutionary death for sin/sinners, resurrection, ascension, dispatching His Spirit), and all who trust Him begin to fulfill Isaiah’s prophecy by making disciples all over the globe.