Canst thou bind the unicorn with his band in the furrow? - That is, with the common traces or cords which are employed in binding oxen to the plow.
Or will he harrow the valleys after thee? - The word "valleys" here is used to denote such ground as was capable of being plowed or harrowed. Hills and mountains could not thus be cultivated, though the spade was in common use in planting the vine there, and even in preparing them for seed, Isaiah 7:25. The phrase "after thee" indicates that the custom of driving cattle in harrowing then was the same as that practiced now with oxen, when the person who employs them goes in advance of them. It shows that they were entirely under subjection, and it is here implied that the ראם re'êm could not be thus tamed.

Canst thou bind the unicorn - in the furrow? - He will not plough, nor draw in the yoke with another? nor canst thou use him singly, to harrow the ground.

Canst thou bind the unicorn with his band in the furrow?.... Put the yoke and harness upon him, and fasten it to the plough to draw it, that he may make furrows with it in the field, or plough up the ground as the tame ox does? thou canst not;
or will he harrow the valleys after thee? draw the harrow which is used after ploughing to break the clods, and make the land smooth and even? he will not: valleys are particularly mentioned, because arable land is usually in them; see Psalm 65:13.

his band--fastened to the horns, as its chief strength lies in the head and shoulders.
after thee--obedient to thee; willing to follow, instead of being goaded on before thee.