In the reaction, H2S + H2O2 → S + 2H2O
H2S is an acid H2O2 is a base
H2S is a base and H2O2 is an acid
H2S is an oxidising agent and H2O2 is a reducing agent
H2S is a reducing agent and H2O2 is an oxidising agent
→ H2S reduces the H2O2 to H2O. Therefore H2S acts as Reducing agent (R.A)
→ H2O2 oxidizes the H2S to S. Therefore H2O2 acts as Oxidizing agent (O.A)