John Gill Commentary Luke 1:79

"To shine upon them that sit in darkness and the shadow of death; To guide our feet into the way of peace." — Luke 1:79 (ASV)

To give light to them that sit in darkness
God's elect among the Jews, who were not only in a state of unregeneracy, which is a state of darkness, ignorance, and unbelief; but in the darkness of the legal dispensation, and at this time under more than ordinary darkness and ignorance; having lost the knowledge of the righteousness of God, and of the spirituality of his law, the true sense of the Scriptures, and right notions of the Messiah; being led by blind guides, the Scribes and Pharisees;

and ,
were as it were also,

in the shadow of death ;
in a state seemingly irrecoverable, when Christ, the great light arose, and shone upon them; and communicated spiritual light, life, and heat unto them; see (Isaiah 9:2) compared with (Matthew 4:13–16) though Christ is also a light, to lighten his chosen ones among the Gentiles, (Luke 2:32) but the Jews seem chiefly to be intended here:

to guide our feet into the way of peace ;
which we knew not: not that he came to teach us how to make our peace with God, but to make peace for us, by the blood of his cross; and so by his Spirit and word, lead us into the true way of enjoying spiritual peace here, and eternal peace hereafter.