(29) Thou art my lamp.--Comp. Psalm 27:1. The psalm changes the figure, "thou wilt light my candle (margin, lamp)." With this comp. Psalm 132:17; 1Kings 11:36; 1Kings 15:4.

Verses 29-31. -

"For thou, Jehovah, art my Lamp;
And Jehovah will make my darkness light.
For by thee do I run upon a troop;
In my God I leap over a wall.
God - his way is perfect;
The word of Jehovah is purified.
He is a Shield to all that trust in him." Lamp. The lamp burning in the house is the proof of life and activity present there; and thus the extinguishing of the lamp means ruin and desolation (Job 21:17). So David is called "the lamp of Israel" (2 Samuel 21:17), because the active life of the nation centred in him. In a still higher sense the life and being of his people centres in God, and without him the soul is waste and void, like the universe before God said, "Let there be light." I run. To the warrior in old time speed was as important as strength, and thus Homer constantly calls Achilles "fleet of foot." It was his fleetness which gave Asahel a high place among the mighties (2 Samuel 2:18), and to this quality David now refers. The troop signifies a light armed band of marauders, whom with God's aid David could overtake, and stop in their course of rapine. The wall means fortifications like those of Jerusalem (2 Samuel 5:7). Sieges were tedious affairs in old time, but David had captured that city with a rapidity so great that the metaphor in the text is most appropriate. Purified; or, refined. This does not mean that it is proved by experience and found true, but that it is absolutely good and perfect like refined gold (see Psalm 12:6).

22:1-51 David's psalm of thanksgiving. - This chapter is a psalm of praise; we find it afterwards nearly as Ps 18. They that trust God in the way of duty, shall find him a present help in their greatest dangers: David did so. Remarkable preservations should be particularly mentioned in our praises. We shall never be delivered from all enemies till we get to heaven. God will preserve all his people, 2Ti 4:18. Those who receive signal mercies from God, ought to give him the glory. In the day that God delivered David, he sang this song. While the mercy is fresh, and we are most affected with it, let the thank-offering be brought, to be kindled with the fire of that affection. All his joys and hopes close, as all our hopes should do, in the great Redeemer.For thou art my lamp, O Lord: and the Lord will lighten my darkness. See Gill on Psalm 18:28.