The unwanted suitors in Ithaca (in Homer’s Odyssey) are described as eating and drinking up all the wealth of the household, as they wait for Penelope to make a decision about whether to remarry. Mulligan has no compunction about living off the charity of others, which is even more galling when you consider that he’s clearly from a higher social class and greater family wealth than Stephen. That Stephen is asked for the key and the two pence for a pint is his final indignity of the chapter.
For any of you interested in money, rest assured that Joyce keeps careful track of it throughout the novel. Whether it was part of his quest for verisimilitude or just his own cash consciousness, the novel frequently mentions prices charged and amounts paid. There’s even a (more or less) complete budget of Leopold Bloom’s spending at one point. In this chapter, we’ve seen the milkwoman already perform an elaborate calculation of the tower’s milk bill.
Mulligan’s priestly quote is a travesty of Proverbs 19:17 “He that hath pity on the poor lendeth unto the Lord,” done in the manner of Nietzsche’s Zarathustra. By taking Stephen’s money, Mulligan is, in a sense, stealing from the poor indeed.