Albert Barnes Commentary Isaiah 12:2

"Behold, God is my salvation; I will trust, and will not be afraid; for Jehovah, [even] Jehovah, is my strength and song; and he is become my salvation." — Isaiah 12:2 (ASV)

Behold, God is my salvation - Or, God is the author, or source, of my salvation. It has not been brought about by any human hands, but is to be traced directly to Him. The value of a gift is always enhanced by the dignity and excellence of the giver, and it confers an inestimable value on the blessings of salvation that they are conferred by a being no less than the infinite God. It is not by human or angelic power; but it is to be traced directly and entirely to Yahweh.

I will trust, and not be afraid - Since God is its author; since He is able to defend me and to perfect that which He has begun, I will confide in Him and not be afraid of the power or machinations of any enemy. In His hands I am safe. God is the foundation of our confidence; and trusting in Him, His people shall never be moved.

For the Lord Jehovah - This is one of the four places in which our translators have retained the original word Yahweh, though the Hebrew word occurs often in the Scriptures. The other places where the word Jehovah is retained in our version are (Exodus 6:3); (Psalms 68:18); Isaiah (Psalms 26:4). The original in this place is יהוה יה yâh yehovah.

The word יה yâh is an abbreviation of the word Yahweh. The abbreviated form is often used for conciseness, particularly in the Psalms, as in the expression “Hallelujah” (הללוּ־יה halelû-yâh), that is, praise Yahweh (Psalms 89:9; Psalms 94:7, 12; Psalms 104:35; Psalms 105:15; Psalms 106:1, 48; Psalms 111:1; Psalms 113:1, and others).

In this place and in Isaiah 26:4, “the repetition” of the name seems to be used to denote “emphasis;” or perhaps to indicate that Yahweh is the same always—an unchangeable God. In two codices of Kennicott, however, the name יה yâh is omitted, and it has been conjectured by some that the repetition is an error of transcribers; but the best MSS. retain it. The Septuagint, the Chaldee, and the Syriac, however, omit it.

Is my strength and my song - The same expression occurs in the hymn that Moses composed after the passage of the Red Sea, in imitation of which this song is evidently composed (Exodus 15:2):

Jehovah is my strength and my song,
And he is become my salvation.

The word ‘strength’ means that He is the source of strength, and implies that all who are redeemed are willing to acknowledge that all their strength is in God. The word ‘song’ implies that He is the proper object of praise; it is to celebrate His praise that the ‘song’ is composed.

He also is become my salvation - This is also found in the song of Moses (Exodus 15:2). It means that God had become, or was the author of salvation. It is by His hand that the deliverance has been effected, and to Him should be the praise.