What are the three comparisons in the Book of Changes?

There is no such thing as Sanbi in the Book of Changes.

The source of this word is the nine planets of Daoism and Magic Road (that is, the Big Dipper plus two small stars invisible to the naked eye, called Zuo Fu, Youbi and Yi ***9 respectively), and then the nine planets are assigned to the special ninth house, so there is:

"Nine palaces, one white, two black, three blue and four green, Huang Wu, six white, seven red and eight white nine purple, Taoism bearing the 89 planetary gate, eight bullying the gods, laying three strange and six instruments, so nine palaces are the carrier of the acquired strange patterns, based on shape, bearing everything and carrying the sky."

The full text is the application of nine planets fabrics in Jiugong, and Sanbi is the name of one of them.

As for why it is called this name, it is because of the faction of mathematics. It is called no in different factions, but it refers to these nine stars.

So Sanbi is the name of a star in the Big Dipper.