Halakhah for Bava Metzia 221:20

To not oppress: To not hold on to that which is in our hand of someone else's by way of force or delay or deception - like delinquents who delay people, saying, "Go and return," so as to cause that what is in their hand of someone else's to remain with them. And this is an extremely bad trait, and [so] our perfect Torah distanced us from it and warned us about it in this place, as it is written (Leviticus 19:13), "You shall not oppress your neighbor" - as one who holds the money of someone else in this manner that we said is called an oppressor. And also included in oppression is anyone who is liable specific money to his fellow and he oppresses him, such as one who suppresses the wage of a wage worker and similar to it. As we do not require that the money actually come from the hand of the oppressed to the hand of the oppressor; but rather anyone that has a claim of specific money against him and he delays it as a result of his violence or any angle of deception is called an oppressor. And even though oppression, robbery and theft are one matter even if the act of one is different from the another, as the intention of the three of them is that a man not take that which is someone else's in any way; since people pilfer each other in these three ways, Scripture specified all of them and warned about each one on its own. And similar to this is what they, may their memory be blessed, said in Metzia (Bava Metzia 111a), "Rava said, 'This is oppression, this is [also] robbery. And [so] why did Scripture divide them [and specify each one]? To [have one who commits it] transgress two negative commandments.'"