What does Psalm 139:11 mean?
David understood that the Lord was watching over him. Even the darkness could not conceal him from God's watchful eye."Darkness" is often associated with death. Psalm 88:3–5 refers to death as Sheol, the pit, and the grave. The psalmist of that passage, Heman the Ezrahite, writes in verse 6, "You have put me in the depths of the pit, in the regions dark and deep." Perhaps what Heman referred to in Psalm 88 is trouble that seems like a death sentence.
As Psalm 121:3–4 points out, God guards His people and will not doze off or fall into a deep sleep. He is always alert to what is happening in the lives of His people. Jesus said our heavenly Father sees even a sparrow's fall to the ground and knows how many hairs are on our head, therefore we have nothing to fear (Matthew 10:28–31).