The original version of the prhase was "it is a stew for the SOUL". So the proper translation is "Feijoada é um guisado para a alma". (please see the point 3, the prhase "Feijoada é um guisado pela alma" is not grammatically wrong but the meaning is totally different)
- The preposition 'PARA', depending of the context it can be translated as "To", "In order to", "forward", "for". It is used to indicate the final destiny, recipient, deadline and to indicate goals.
- The preposition 'POR', depending of the context it can be translated as "By", "Through", "For". It is used to indicate the duration of a period, the way used to reach the final destiny, in passive voice sentences indicating the doer (the active person) of an action.
- 'PELA' is the contraction of 'POR + A'.
Considering the definitions of 'POR' and 'PARA' and that "FOR" is a mutual translation for both, if you say:
- "Feijoada é um guisado para a alma" the idea is that the feijoada is made for the soul. So, I think is the idea of the original prhase in English.
- "Feijoada é um guisado pela alma" (POR+A): you are giving the idea that the essence of feijoada is being a stew (well, at least a poetic way to say this, is not a common usage). And I think the English prhase for the use of "PELA" in this context would be "Feijoada is a stew by its SOUL"
P.S.: I want to take this opportunity and apologize, because as your original prhase was not grammatically incorrect, I did not notice the original translation.