When his candle shined upon my head, and when by his light I walked through darkness; When his candle shined upon my head - Alluding most probably to the custom of illuminating festival or assembly rooms by lamps pendant from the ceiling. These shone literally on the heads of the guests.
By his light I walked through darkness - His light - prosperity and peace - continued to illuminate my way. If adversity came, I had always the light of God to direct me. Almost all the nations of the world have represented their great men as having a nimbus or Divine glory about their heads, which not only signified the honor they had, but was also an emblem of the inspiration of the Almighty.