Gentling the Bull is the fifth of the Ox- herding pictures which is a series of paintings and associated  poems describing the terrain and steps of the Way.  The Ox-herding pictures go back to the 8th century and though the progression is presented in a linear fashion, this can never be quite the case. Nevertheless, they intuitively and accurately describe a journey which is timeless.
This practice represented by the fith Ox- herding picture is called  “Gentling or taming the Bull.”  This is the practice of becoming conscious of  the conditioned and mechanical aspects of the self that claim the realization process as theirs and turn buddha-hood into ego-hood.
This gentling stage in the training, which requires objectivity toward oneself  and discipline,  is difficult and often overlooked to the detriment of  students and teachers.

The third stanza of the poem that accompanies the fifth Ox- herding picture is:
In patient training the bull got used to the herdsman and is truly gentle.
Should he now walk into the dust, he no longer gets dirty.
Long and patient gentling! In one sudden plunge the
herdsman has won his whole fortune.
Under the trees, others encounter his mighty laugh.

Gentling the Ox is obtaining power over the conditioned self,  not power over others.  How sad it is, what folly to mistake this point.
Long and patient gentling.   A deep and profound  pleasure.
The Ox transforms into a magic horse.