Commentary for Isaiah 27:5

If they would grasp My fortress (אוֹ), lit., or they would grasp My fortress,) an expression of ‘if.’ Comp. “(Ex. 21:36) If (אוֹ) it was known that he was a goring ox.” If My people grasp My fortress, i.e., My Torah, that they seek no other fortress but My fortress, then they shall grant Me peace, to calm My thoughts and My ire which trouble Me because I do not avenge Myself upon My adversaries, and I will, indeed, take revenge from them.

Or let him take hold, etc. Or let the Israelites take hold of my strength, then I shall not have war with them—comp. the Lord hath been like an enemy (Lam. 2:5)—

they would make peace for Me from the standard of justice, so that it will be unable to accuse and to say, “Why are these different from those?” (I.e., Why are the Jews different from the other nations?)