Indeed It Is Through God That We Will Triumph (Psalms 18:28-29).
‘For you will light my lamp,
YHWH my God will lighten my darkness.
For by you I run on a troop,
And by my God do I leap over a wall.
Here is the Godward side. David is confident that it is God Who will deliver him. Note that his reliance is all on God. It is He Who will light his lamp, showing him the way in the darkness and giving him guidance as to how he should walk, and illumination as he seeks God. What seemed at the time dark around him would be illuminated by God. ‘God is light' said John (1 John 1:5), ‘and in Him is no darkness at all'. And David had found it true in experience. It was because God had shone within him, and would continue to shine within him, that he had hope. What he was, was because God had shone within him. Note the change from ‘you' to ‘YHWH my God'. As he speaks man to God he is suddenly filled with awe to think Who it is he is speaking to. It is not just anyone, but YHWH, Who will lighten his darkness.
There may be here the thought of the lamp in the Tabernacle which was lit daily in the evening (Exodus 30:8) to represent God as a light to His people. As each day began the lamp was lit, the lamp that illuminated Israel. God's illumination was continually with them, repeatedly renewed, and he shone out for them. So was David confident that He would light his lamp daily too.
‘For by you I run on a troop, and by my God do I leap over a wall.' The twofold thought here is of success in warfare. He had not chosen warfare but it had been forced on him. And he knew that his success had been of YHWH. To run on a troop is to chase, attack and defeat them, as he did the Amalekites (1 Samuel 30), to leap over a wall describes his taking of cities like the Jebusite city of Jerusalem. The walls were no hindrance to him. He, as it were, simply leapt over them. And it was because YHWH was with him. He gave all the glory for his success to God.
And it will ever be thus. The singers were confident, as they entered into David's experience, and we too may be sure, that whatever foe we face, whatever obstacle lies before us in the spiritual realm we also can ‘run on' them or ‘leap over' them by the power and sustenance of God.