The pillars of heaven tremble. The "pillars of heaven" are the mountains, on which the sky seems to rest. These "tremble," or seem to tremble, at the presence of God (Psalms 18:7; Psalms 114:4; Isaiah 5:25) when he visits the earth in storm and tempest, either because the whole atmosphere is full of disturbance, and the outline of the mountains shifts and changes as rain and storm sweep over them, or because the reverberations of the thunder, which shake the air, seem to shake the earth also.
And are astonished at his reproof. To the mind of the poet this "trembling" is expressive of astonishment and consternation. He regards the mountains as hearing the voice of God in the storm, recognizing it as raised in anger, and so trembling and cowering before him.