Zhouyi BenyiLine statement
'Gu' (牿) is pronounced with the fanqie gu-du. A young ox (tong) refers to one whose horns have not yet grown. A 'gu' is a crossbar affixed to the horns of an ox to prevent it from goring, what the Book of Songs calls the 'fuheng' (crosspiece).
Restraining it before its horns have grown requires little effort, bringing supreme goodness and good fortune; hence its image and divination are such. The Record of Learning states: 'Prohibiting before things occur is called foresight'—this is precisely the meaning.
'Fen' (豶) is pronounced with the fanqie fu-yun.
When yang has already advanced, restraining it is not as easy as at the beginning; however, dwelling in the Central Position with yielding nature and occupying the position of honor, one grasps the opportune moment and can subdue it.
Hence its image is like this; though the divination is auspicious, it does not say 'supreme.'