3 CuS-II + 8 HNVO3 3 Cu(NVO3)2 + 3 S0 + 2 NIIO + 4 H2O

This is an oxidation-reduction (redox) reaction:

3 S-II - 6 e- 3 S0 (oxidation)

2 NV + 6 e- 2 NII (reduction)

CuS is a reducing agent, HNO3 is an oxidizing agent.