‘And in that day you will say,
Give thanks to Yahweh,
Call on his name,
Declare his doings among the peoples,
Make mention that his name is exalted.'
Sing to Yahweh, for he has done excellent things,
Let this be known in all the earth.
Cry aloud, and shout, you inhabitant of Zion,
For great is the Holy One of Israel in the midst of you.'
The first part of the song looked at themselves, now they look out so that the world might praise Him. They point to His activity, and all that He has done, and cry out that it should be publicised among the nations, so that His name might be exalted by all men.
‘Give thanks to Yahweh, call on His name.' This parallels ‘sing to Yahweh'. Thus it is a calling of gratitude, worship and praise, to be followed by a declaration of all that God has done so that the whole world might know of His doings.
And lastly he calls on Israel/Judah, the inhabitant of Zion, to fulfil their function, and like a town crier, shout out about their God, because of the greatness of the One Who is among them, ‘the Holy One of Israel.'
So Isaiah ends this section with ‘the Holy One of Israel' resident among His made-holy people. All that Chapter s 6-11 have led up to is summarised in this. God's triumph and purpose is complete.