Charles Ellicott Commentary Job 39:9

"Will the wild-ox be content to serve thee? Or will he abide by thy crib?" — Job 39:9 (ASV)

The unicorn. —It is a mistake to identify this animal with the rhinoceros, as was formerly done; it is more probably the same as the buffalo, or wild ox. The most glaring form of the mistake is in Psalm 22:22: Thou hast heard me also from among the horns of the unicorns.

The way in which the animal is here spoken of, as in analogous contrast to the domestic ox, suggests that it is not wholly dissimilar. It is familiar and domestic toil that the wild ox is contemplated as undertaking, in the place of tame cattle, whose work it is.