‘YHWH is in his holy temple,
YHWH, his throne is in heaven,
His eyes behold, his eyelids try,
The children of men.
The psalmist now turns from the challenge that has been put to him and the reply he has given, to the God in Whom he trusts, the God Who is his refuge. He knows that he does not need to defend himself in this case for YHWH is over all. He is on His heavenly throne (Psalms 9:4; Psalms 9:7), and from His heavenly Temple He watches over His people (compare 1 Kings 8:26 onwards) and over him. Indeed His eyes behold all men, and His eyelids test them out, so that the wicked are under His eye too. He knows all that they do. The idea behind the eyelids is that when we are carefully peering at something we tend to contract the eyelids. So God peers at the behaviour of men carefully and constantly. The word for testing out is used of the refining of metals. At a glance YHWH can distinguish what is true from what is base, for YHWH has an all-seeing eye.
For His Temple as signifying Heaven see also Psalms 18:6; Psalms 29:9; Micah 1:2; Habakkuk 2:20 compare also Psalms 9:7 with 11. This is a reminder that the earthly Temple was always seen as but a shadow of the heavenly, a kind of way by which His people could approach the heavenly Temple through the earthly (1 Kings 8:26 onwards). This was what was in Ezekiel's mind when he spoke of the heavenly Temple descending on an anonymous high mountain, a pure and heavenly Temple accessible through the earthly altar in the physical Temple, the altar which men were commanded to build (they were not commanded in Ezekiel to build a Temple, only the altar).