Shylock says this of Antonio in Act 1, Scene 3. Here are lines 38 - 43:
I hate him for he is a Christian;
But more, for that in low simplicity
He lends out money gratis and brings down
The rate of usance here with us in Venice.
If I can catch him once upon the hip,
I will feed fat the ancient grudge I bear him.
"Catch him upon the hip" is a figure of speech from wrestling. Apparently it means to gain an advantage over him, as if to throw him to the ground. So far, Shylock has been unable to gain any kind of hold on Antonio to do him harm, but now he sees his chance.
Shylock does not just hate Antonio on principle for being a Christian. He has a personal hatred for him. He feels as if he and Antonio have been wrestling each other for control of the money market in Venice. Antonio is willing to lend money at no interest, and this makes it harder for Shylock to charge interest and make a living. Apparently, this has been going on for some time. In another place, Antonio tells us that Shylock hates him because Antonio has sometimes come to the rescue of people who owed large sums to Shylock.