Isaiah 11:13 - Matthew Poole's English Annotations on the Holy Bible

Of Ephraim, i.e. of the ten tribes, frequently called by the name of Ephraim, as hath been already and frequently observed, between whom and Judah there were great emulations and contentions. Shall depart; of enemies they shall be made friends, and of wolves lambs, as was said before on Isaiah 11:6; they shall be united together in one church, under the Messiah, keeping the unity of the Spirit in the bond of peace. The adversaries of Judah; not the body of Ephraim, for they are supposed to be reconciled, and they shall not be cut off, but live in love with Judah, as we see by the next clause; but those few of them which possibly may continue in their enmity against them, together with all the rest of their adversaries. Ephraim shall not envy Judah, and Judah shall not vex Ephraim; not only all outward hostilities shall cease, but also their inward animosities.