The various possible identities of the creature referred to next are considered by Gill. The KJV has the mythical ‘unicorn’, and yet this was certainly not a mythical creature but one known to Job at least by report.
The lesson from the wild ox is that there are forces at work which are impossible for Job to tame and make use of. The wild ox is a creature of great strength, but man cannot harness its strength. Consider the wild ox – what good are it doing? What is the use of it being so strong if it only wanders about and eats? The frustration of this is that you cannot harness its power. Will it stand by your bed, plough for you, or remain where you put it? It is more likely to eat what it wants, and kick over any fences erected to contain it. Job, you have overestimated your powers. There are many things you cannot do; you need a greater sense of perspective. God enables his children to do much, and there are certain powers resident in us from the moment of conversion, but still we need the help and power of God for so much more. We are dependent on him to contain the great forces which are against us, for we cannot defeat them in our own strength. Satan is an adversary who will certainly will overcome – in spite of our weakness – but we will only do it by the help of the Lord, not because we have prevailed against him ourselves. I cannot defeat the devil without prayer and in God’s good time.