To give light to them that sit in darkness and in the shadow of death, to guide our feet into the way of peace.
All Commentaries on Luke 1:79 Go To Luke 1
John Chrysostom
AD 407
By darkness he means not material darkness, but error or and distance from the faith, or ungodliness.
He rightly says sitting, for we were not walking in darkness, but sitting down as having no hope of deliverance.