heifer - wanton, like a fat, untamed heifer (Hos 10:11). Appropriate to Egypt, where Apis was worshipped under the form of a fair bull marked with spots.
destruction - that is, a destroyer: Nebuchadnezzar. Vulgate translates, “a goader,” answering to the metaphor, “one who will goad the heifer” and tame her. The Arabic idiom favors this [Rosenmuller].
cometh ... cometh - The repetition implies, it cometh surely and quickly (Psa 96:13).