Wilt thou trust him? - As thou dost the ox. In the domestic animals great confidence is of necessity placed, and the reliance on the fidelity of the ox and the horse is not usually misplaced. The idea here is, that the unicorn could not be so tamed that important interests could be safely entrusted to him.
Because his strength is great? - Wilt thou consider his strength as a reason why important interests might be entrusted to him? The strength of the ox, the camel, the horse, and the elephant was a reason why their aid was sought by man to do what he could not himself do. The idea is, that man could not make use of the same reason for employing the rhinoceros.
Wilt thou leave thy labour to him? - Or, rather, the avails of thy labor - the harvest.

Wilt thou trust him, because his strength is great?.... No; tame oxen are employed because they are strong to labour, Psalm 144:14; and they are to be trusted, in ploughing or treading out the corn, under direction, because they are manageable, and will attend to business with constancy; but the wild ox, though stronger, and so fitter for labour, is yet not to be trusted, because unruly and unmanageable: if that sort of wild oxen called "uri" could be thought to be meant, for which Bootius (h) contends, Caesar's account of them would agree with this character of the "reem", as to his great strength: he says of them (i), they are in size a little smaller than elephants, of the kind, colour, and shape of a bull; they are of great strength and of great swiftness, and not to be tamed;
or wilt thou leave thy labour to him? to plough thy fields, to harrow thy lands, and to bring home the ripe corn? as in Job 39:12; thou wilt not.
(h) Animadvers. Sacr. l. 3. c. 1. s. 14. (i) Comment. de Bello Gall. l. 6. c. 27.

thy labour--rustic work.