Psalm 139:11-12 meaning

David continues his account of God's omnipresence (His existence in all places always) and omnipotence (His power over all things), combining the two. David begins to talk about a contrast between light and darkness, which is likely a metaphor for the ongoing conflict between good and evil in this world. The darkness seems to always be lurking at the edge of the light, threatening to encroach upon it. Similarly, David expresses how he feels about the ever-looming evil around him.

Sometimes, we imagine that the darkness will overwhelm us and that we will be unable to escape it. In other words, it seems as though it is impossible to stave off evil any longer. If we make a misstep, we feel as though we will be overwhelmed by its power. Other times, we feel as though the darkness will envelop us, and consume the light around us. Thus it will be night, and the darkness will snuff out the light. But David acknowledges that this is a limited perspective.

In the next verse, David asserts that even the darkness is not dark to God. The character of God, who has power over all things is not stopped by darkness. To Him, the night is as bright as the day. God is not only in control of light and darkness, but He is the light of the world and those who follow Him "will not walk in the darkness but will have the Light of life" (John 8:12).

The darkness is illuminated by His mere presence. So there is no way for us to hide in the darkness, or for the darkness to overcome us. Anywhere that His people go, the God who can enter all places and who has power over them, can go too. John 1:5 says that "The Light shines in the darkness, and the darkness did not comprehend it." In other word, the power of God's light is so great that darkness and light are alike to Him, equally under His control. This means that God's light is always with us, even when we cannot perceive it with our physical eyes.