Behold even to the moon, and it shineth not - Or, behold even the moon shineth not. That is, in comparison with God it is dark and obscure. The idea is, that the most beautiful and glorious objects become dim and fade away when compared with him. So Jerome renders it, Ecce luna etiam non splendet. The word here rendered “shineth” (יאהיל ya'âhalı̂yl) frequently means to pitch or remove a tent, and is a form of the word אהל 'ôhel uniformly rendered tent or tabernacle. Some have supposed that the meaning here is, that even the moon and the stars of heaven - the bright canopy above - were not fit to furnish a tent or dwelling for God. But the parallelism seems to demand the usual interpretation, as meaning that the moon and stars faded away before God. The word אהל 'ôhel derives this meaning, according to Gesenius, from its relation to the word הלל hâlal, to be clear or brilliant, from the mutual relation of the פא and עע verbs. The Arabic has the same meaning.
Yea, the stars are not pure in his sight - That is, they are not bright in comparison with him. The design is to show the glory of the Most High and that nothing could be compared with him; see the notes at Job 4:18.