Na2SO3 (aq) + Fe2(SO4)3 (s) + H2O (l) → Na2SO4 (aq) + 2 FeSO4 (aq) + H2SO4 (aq)
This is an oxidation-reduction (redox) reaction:
SIV - 2 e- → SVI (oxidation)
2 FeIII + 2 e- → 2 FeII (reduction)
Na2SO3 is a reducing agent, Fe2(SO4)3 is an oxidizing agent.