You will say in that day: “I will give thanks to you, O Lord, for though you were angry with me, your anger turned away, that you might comfort me.
“Behold, God is my salvation; I will trust, and will not be afraid; for the Lord God is my strength and my song,and he has become my salvation.”
With joy you will draw water from the wells of salvation. And you will say in that day:
“Give thanks to the Lord, call upon his name, make known his deeds among the peoples, proclaim that his name is exalted.
“Sing praises to the Lord, for he has done gloriously; let this be made known in all the earth. Shout, and sing for joy, O inhabitant of Zion, for great in your midst is the Holy One of Israel.” (Is. 12)
Following on the heels of the prophecies of the coming Messianic Kingdom of our Lord Jesus Christ comes an outpouring of praise. Isaiah representing the people of God praises and thanks God for how good he is in averting His anger from us. As formerly God's people were subjected to God's wrath and punishment, yet now God's anger has turned away and He is there to comfort us once again. God indeed is our salvation, our strength and our song who works all things together for our good (cf Rom. 8:28). For God in the Messiah has reconciled His people to Him (2 Cor. 5:19) and therefore we are no more under His wrath. Because Jesus is spotless and His propitiation perfect, therefore our salvation is assured and we can completely trust God for it. Therefore, we can praise God for His exceedingly great salvation He has wrought for us.
Such a reality is indeed cause for joy, for we who were once under God's judgment because of our sins are now saved from it by God's grace (v. 3; cf Rom. 5:8-9), with the resultant overflowing of that joy in exalting His name among the nations and making known His deeds (v. 4). Historically, this shows the global scope of Israel's mission, which is to glorify God's name among the nations, which she failed to do time and time again. Nevertheless, God is not limited to Israel's failures and His cause would spread into the nations with or without Israel, as indeed it happened when Israel rejected her Messiah.
So let us come and sing and shout for joy to God (v. 5) for God the Holy One is in our midst (v. 6), for us and not against us. Amen and Amen!