The two substances that react together to make sodium chloride (NaCl) and water (H₂O) are sodium hydroxide (NaOH) and hydrochloric acid (HCl).

This is a classic example of a neutralization reaction, where an acid (HCl) reacts with a base (NaOH) to produce salt (NaCl) and water (H₂O).

The balanced chemical equation for this reaction is:

NaOH + HCl → NaCl + H₂O