In IRL witchcraft, Wicca in particular, the "reciprocity law" is an actual real thing. We call it the rule of threefold-- but we use it for everything, not just magick. It's basically a personal karma system.
"Mind the three-fold laws, you should three times bad and three times good."
Basically, you do something nice for/to me, I repay you with something better. Same goes for bad. Bake me cookies? I invite you for a nice dinner. You steal from me, I get you fired.