Isaiah 8:2,3 - Joseph Benson’s Commentary on the Old and New Testaments

And I took me faithful witnesses Persons of unquestionable reputation, who should bear witness that the following name and prophecy were written and published by me, according to God's command. It is likely these witnesses signed a copy of the prophecy with their own hands, and dated it according to the time it was declared by the prophet. And I went unto the prophetess His own wife, so called, because she was the wife of a prophet, wives being frequently denominated from their husband's titles. Or possibly she herself might be endowed with the gift of prophecy. Some commentators suppose that Isaiah married another wife on this occasion, and that the witnesses above mentioned were called to attest the matrimonial contract, according to the custom of the Jews. But there are no indications of this, and, as it is certain from the preceding chapter that he already had a wife, the mother of Shear-jashub, it seems highly improbable that he should take another. Others again suppose, that these witnesses, who were persons of rank, “were called on to attend the circumcision of the prophet's son, and to attest the name by which he was called, as well as the prophecy, confirmed and illustrated by that name.”