In The Merchant of Venice, what is Shylock's motive for setting up the bond between Antonio and himself?

I assume that your question is asking why Shylock loans
Antonio the money and why he makes this deal where the collateral will be a pound of
Antonio's flesh.  If so, the motive is Shylock's hatred for Antonio.  Shylock is hoping
that the ships will not come in and he will be able to hurt (and probably kill)
Antonio.

As to why Shylock hates Antonio, that is less
clear.  Shylock himself says various things.  He says that he hates Antonio because he
is Christian.  He says he hates Antonio for lending money without charging for it.  He
says he hates Antonio for no clear reason.  All of these may be true.  However, it seems
likely that he hates Antonio because Antonio has treated him badly.  This is the most
likely reason for Shylock to hate Antonio.  It is this hatred that causes him to set up
the bond between Antonio and himself.