This is Elijah (αυτος εστιν Ελειας). Jesus here endorses John as the promise of Malachi. The people understood Malachi 4:1 to mean the return of Elijah in person. This John denied as to himself (John 1:21). But Jesus affirms that John is the Elijah of promise who has come already (Matthew 17:12). He emphasizes the point: "He that hath ears to hear, let him hear."