First of all, assign oxidation number to each of the species in the given reaction.
\(2\overset{+1}{Cu}_2\overset{-2}{O}(s)+\overset{+1}{Cu_2}\overset{-2}{O}(s)\rightarrow6\overset{o}{Cu}(s)+\overset{+4}{S}\,\overset{-2}{O}(g)\)
So, it is concluded that in this reaction, copper is reduced from +1 oxidation state to zero oxidation state and Sulphur is oxidised from -2 oxidation state to +4 oxidation state.
Hence, this reaction is a redox reaction.
Further, Cu2O is used to oxidise Sulphur. So, Cu(l) is an oxidant and Sulphur of CuS is used to reduce copper both in CuS itself and Cu2O to decrease its oxidation number, so, Sulphur of Cu2S is a reductant.