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.
Behold, God [is] my salvation
Or Saviour; that is, Christ, who is God, the great God, and so fit to be a Saviour, and is one, was appointed by the Father, provided in covenant, promised in the word, sent in the fullness of time, and is become the author of salvation, which a creature could not be; and this the church saw her interest in, and which was the ground of her comfort before declared; and to which she prefixed the word “behold”, as a note of asseveration, affirming him to be her Saviour; and of admiration, wondering at it; and of exclusion of all others from being concerned therein; and of attention and direction to others, pointing him out as the only one to look unto.
I will trust, and not be afraid;
“trust” in Christ for salvation, be confident of enjoying it, and look upon myself safe and secure from all wrath and condemnation, and from every enemy; and not be “afraid” of sin, Satan, the world, death, hell, and wrath to come. The Targum joins this and the preceding clause together,
“behold, in the word of God my salvation I trust, and shall not be moved:”
for the LORD JEHOVAH [is] my strength and [my] song;
the author of her spiritual strength; the “strength” of her life, and of her heart, which maintained the one, and supported the other; the strength of her graces, and of her duties, by which she exercised the one, and performed the other: and the subject matter of her “song” were his person, and the fullness and fitness of it, his righteousness, and salvation by him; this clause, and the following one, are taken out of (Exodus 15:2):
He also is become my salvation;
salvation is wrought out by Christ, and believers have it in him, and they know it, and believe it, and so are already saved in him.
John Gill’s Exposition of the Bible