I₂⁰ + Cl₂⁰ + 2 H₂O → 2 HI^IO + 2 HCl^-I

This is an oxidation-reduction (redox) reaction:

2 I⁰ - 2 e^- → 2 I^I (oxidation)

2 Cl⁰ + 2 e^- → 2 Cl^-I (reduction)

I₂ is a reducing agent, Cl₂ is an oxidizing agent.