The LORD is in His holy temple, the LORD’s throne is in heaven; His eyes behold, His eyelids test the sons of men.
Psalm 11 starts with David stating his trust in God, but quickly moves into contemptuous challenges thrown at him by the wicked (verses 1-3).
David replies with assurance that God is in charge. He knows what is going on, and He can provide refuge from their arrows and their taunts. As Matthew Henry’s Commentary puts it, “The Lord is in his holy Temple above, where, though he is out of our sight, we are not out of his. … He not only sees them, but he sees through them, not only knows all they say and do, but knows what they think, what they design, whatever they pretend.”
For more about the trust we can have in God, see “What Is Faith?”