The Scofield Bible Commentary, by Cyrus Ingerson Scofield, , at sacred-texts.com
Prayer in the Old Testament is in contrast with prayer in the New Testament in two respects:
(1) In the former the basis of prayer is a covenant of God, or an appeal to his revealed character as merciful, gracious, etc. In the latter the basis is relationship: "When ye pray, say, Our Father" (Mat 6:9).
(2) A comparison, for example of the prayers of Moses and Paul, will show that one was praying for an earthly people whose dangers and blessings were earthly; the other for a heavenly people whose dangers and blessings were spiritual.
at the light
Or, thine arrows walked in the light, etc.
That is, despite the afflictions of Israel in dispersion, the prophet will rejoice because of the Lord, as yet to return to His temple.