“And in that day thou shalt say, O LORD, I will praise Thee: though Thou wast angry with me, Thine anger is turned away, and Thou comfortedst me. Behold, God is my salvation; I will trust, and not be afraid: for the LORD JEHOVAH is my strength and my song; He also is become my salvation. Therefore with joy shall ye draw water out of the wells of salvation.” Isaiah 12:1-3 (KJV)
“That day” spoken of is carried over from chapter eleven, and has to do with that day when the Messiah of Israel returns to earth, and sets up His kingdom.
In that day will be a wonderful day of salvation for the nation of Israel. They will sing a song similar to the song of Moses and of Miriam (Exodus 15).
The MacArthur Study Bible note says, “They are the earthly counterpart to the heavenly doxology in Rev. 19:6, 7”
One thing I noticed as I read verse 2 above was the use of the name “LORD JEHOVAH”. “LORD” is the shortened “Jah” name of Jehovah, and “JEHOVAH” is the full name. It is given to give us double assurance of who God is; and that He is the covenant keeping GOD.
For the Christian today we can rest in the assurance of who God is. He is our strength and our song. He is also our salvation. We can be assured that He will redeem Israel; and keeping His covenant with Israel is an assurance He keeps His covenant with all who trust in His Son Jesus.