C. F. Keil and Franz Delitzsch on Isaiah 54:6

Isa 54:6

And this relation He now renews. “For Jehovah calleth thee as a wife forsaken and burdened with sorrow, and as a wife of youth, when once she is despised, saith thy God.” The verb קרא, which is the one commonly used in these prophecies to denote the call of grace, on the ground of the election of grace, is used here to signify the call into that relation, which did indeed exist before, but had apparently been dissolved. קראך is used here out of pause (cf., Isa 60:9); it stands, however, quite irregularly for the form in ēkh, which is the one commonly employed (Jdg 4:20; Eze 27:26). “And as a wife:” ואשׁת is equivalent to וּכאשׁת. The hypothetical תמּאס כּי belongs to the figure. Jehovah calls His church back to Himself, as a husband takes back the wife he loved in his youth, even though he may once have been angry with her. It is with intention that the word נמאסה is not used. The future (imperfect) indicates what partially happens, but does not become an accomplished or completed fact: He is displeased with her, but He has not cherished aversion or hatred towards her.