PbS (s) + 4H2O2 (aq) -> PbSO4 (s) + 4H2O (l)
PbS has been oxidized to PbSO4.
The oxidation state of sulfur increased from -2 in PbS to +6 in PbSO4.
H2O2 has been reduced to H2O.
The oxidation state of oxygen decreased from -1 in H2O2 to -2 in H2O.
Since oxidation and reduction occurred simultaneously in the reaction, it is a redox reaction.