And the first-born of the poor shall feed - That is, there shall be safety to those parts of Judah which have long been exposed to the invasions of the Philistines. Philistia bordered on Judea, and was constantly making wars upon it, so that there was no safety felt. Isaiah now says, that Hezekiah would so effectually and completely subdue them that there should be no danger from their invasion. The phrase ‘the first-born of the poor’ is an Hebraism, a strong, emphatic expression, denoting those who are the most poor; the most abject sons of poverty; those who have an eminence or a double portion of need, as the first-born among the Hebrews were entitled to special distinctions and privileges. The idea is, that even the most poor and defenseless would be safe.
Shall feed - That is, they shall be supplied with food; they shall feed safely as a flock does that is guarded from wild beasts. They shall be no longer alarmed, but shall dwell in security, peace, and plenty.
And I will kill thy root - The word rendered ‘root’ denotes properly the root of a plant, which being dried up or killed, the plant of course withers and dies. So God says that he would effectually and entirely destroy the power of the Philistines.
Slay thy remnant - That is, shall slay all that pertains to thee. Or, he shall dry up the root, and the branches shall wither and die also. The whole power of the nation shall be withered and destroyed.