What is the best Spanish translation of the English idiom,
What goes around comes around?
Apart from the ones given by user1074377. I'd add these ones:
which means that good actions will lead to good results and bad actios will lead to misfortune, comparing the results with the sowing and the harvest.
which means that bad actions (metaphorically referred as winds) will bring bad results(metaphorically referred as storms).
In Spain "A cada puerco le llega su sábado" is said as
because the day of "San Martín" (November 11th) is a traditional day for the slaughter of that animal. So they compare the day of the slaughter to the day when the person has to pay for his sins.
As suggested by Gonzalo Medina (thanks):
Idioms like this generally don't translate directly to Spanish (or most languages) so there's really not a perfectly equivalent translation.
However, You can take the idea of the proverb and find a proverb that has a similar meaning in Spanish.
Some of my favorites:
You can find heaps of proverbs with same/similar meanings by doing a Google search.