Doth the wild ass bray when he hath grass? - On the habits of the wild ass, see the notes at Job 11:12. The meaning of Job here is, that he did not complain without reason; and this he illustrates by the fact that the wild animal that had a plentiful supply of food would be gentle and calm, and that when its bray was heard it was proof that it was suffering. So Job says that there was a reason for his complaining. He was suffering; and perhaps he means that his complaint was just as natural, and just as innocent, as the braying of the ass for its food. He should have remembered however, that he was endowed with reason, and that he was bound to evince a different spirit from the brute creation.
Or loweth the ox over his fodder? - That is, the ox is satisfied and uncomplaining when his needs are supplied. The fact that he lows is proof that he is in distress, or there is a reason for it. So Job says that his complaints were proof that he was in distress, and that there was a reason for his language of complaint.