R' Yechiel Meir Lifshitz of Gostynin once rebuked a store owner for exploiting the poor and unfortunate people that resided in his town. Instead of showing them mercy, he cruelly charged exorbitant prices for his goods.
R' Lifshitz said to him: "What you are doing is hinted to in a verse. The Torah states: "What gain [betza] will there be if we kill our brother?" [Vayeishev 37:26].
"The acronym of the word "betza" is boker [morning], tzaharayim [afternoon] and erev [evening] - the three periods of the day when a Jew is required to pray to Hashem.
"Now tell me" concluded R' Lifshitz, "mah betza" - why bother [praying three times a day] - "if we kill our brother" - if at the same time we are busy cruelly exploiting our poor and needy brethren."
Source: Rabbi Y. Bronstein