ישעיהו ה:יט פירוש: רש״י ואבן עזרא

Let Him hurry; let Him hasten His deed [i.e.,] the retribution He says He will bring.

ימהר Either transitive, let him bring hastily; comp. מהרו (Esth. 5:5), fetch hastily; or intransitive, let him make speed; and only יחישה transitive, let him accelerate. As to two verbs in the future following each other without conjunction, comp. אל תרבו תדברו Talk no more (1 Sam. 2:3).—Let these prophecies be fulfilled, that we may see whether they are true.

so that we may see whose word will stand up.