ACT II SCENE 1: What do you think “let him look to his bond” means?

SHYLOCK There I have another bad match!—a bankrupt, a prodigal who dare scarce show his head on the Rialto, a beggar that was used to come so smug upon the mart. Let him look to his bond. He was wont to call me usurer; let him look to his bond. He was wont to lend money for a Christian courtesy; let him look to his bond.