20 Consult God’s instruction and the testimony of warning. If anyone does not speak according to this word, they have no light of dawn.

Read Isaiah 8:20 Using Other Translations

To the law and to the testimony: if they speak not according to this word, it is because there is no light in them.
To the teaching and to the testimony! If they will not speak according to this word, it is because they have no dawn.
Look to God’s instructions and teachings! People who contradict his word are completely in the dark.