This collection of songs of praise closes the first part of the book, not unlike the doxologies that close the first four books of the Psalter (Psalms 41:13; 72:18-19; 89:52: 106:48).
"For the LORD GOD is my strength and my might; he has become my salvation" repeats Moses' song of victory after the exodus (Exodus 15:2), just one of many places where Isaiah calls upon the exodus tradition to speak of God's new work of deliverance in his day.
12You will say on that day:
I will give thanks to you, O Lord,
for though you were angry with me,
your anger turned away,
and you comforted me.
2 Surely God is my salvation;
I will trust, and will not be afraid,
for the Lord God * is my strength and my might;
he has become my salvation.
3 With joy you will draw water from the wells of salvation.
4And you will say on that day:
Give thanks to the Lord,
call on his name;
make known his deeds among the nations;
proclaim that his name is exalted.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org