That walk; or, are on their way (comp. Isaiah 31:1). Either the Jewish ambassadors have already started, or the anticipatory vision of the prophet sees them as if starting. In the history (2 Kings 18:13-37; Isaiah 36:1-22) it is not expressly said that Hezekiah made application to Egypt for aid; but the reproaches of Rabshakeh (2 Kings 18:21, 2 Kings 18:24) would be pointless if he had not done so.
Have not asked at my mouth. As they ought to have done (see Numbers 27:21; 1:1; 20:18; 1 Samuel 23:2; 1 Kings 22:7, etc.). To strengthen themselves in the strength of Pharaoh. It is very uncertain who is the "Pharaoh" here intended.
The supreme power over Egypt was probably, at the time, in the hands of Tirkakah (2 Kings 19:9); but Lower Egypt seems to have been ruled by various princes, the chief of whom was Shabatok, and any one of these may have been regarded by Isaiah as a "Pharaoh."
To trust in the shadow of Egypt. Trust in the "shadow of God" was an expression very familiar to the Jews (see Psalms 17:8; Psalms 36:7; Psalms 63:7; Psalms 91:1; Isaiah 25:4; Isaiah 32:2). To "trust in the shadow of Egypt" was to put Egypt in the place of God.