Charles Ellicott Commentary Isaiah 8:20

"To the law and to the testimony! if they speak not according to this word, surely there is no morning for them." — Isaiah 8:20 (ASV)

To the law and to the testimony.—These words are only remotely and by analogy an exhortation to the study of Scripture in general, or even to that of the Law of Moses in particular. “The law and the testimony” are obviously here, as in Isaiah 8:16, the “word of Jehovah,” spoken to the prophet himself—the revelation that had come to him with such an intensity of power.

If they speak not according to this word... —The personal pronoun refers to the people of Isaiah 8:19 who were seeking out soothsayers. The second clause should be rendered, for them there is no light of morning. The light here is that of hope rather than of knowledge. No morning dawn will shine on those who frequented the caves and darkened rooms of the diviners, the séances of the spiritualists of Jerusalem. The verse admits, however, of a different construction.

As the Hebrew idiom, “If they shall ...” stands (Hebrews 4:3; Hebrews 4:5) for the strongest form of negative prediction, so “if they shall not ...” may stand here for the strongest form of positive. Taken this way, the verse would read, Surely they will speak according to this word (that is, will resort to the true Revelation) when there is no morning-dawn for them—when they look above and around and see nothing but darkness.