New Defender's Study Bible Notes
9:13 written of him. Since neither of the Old Testament prophecies of the coming of John the Baptist predict his rejection and martyrdom (note Isaiah 40:3 and Malachi 3:1), this statement (“it is written of him”) must refer only to the phrase “is indeed come.” John came as a type of Elijah’s future coming, but not as the complete fulfillment of Malachi’s prophecy (Malachi 4:5), for Christ also said that Elijah was still to come, even after John had died (Matthew 17:11). See notes on Matthew 17:10-12).
9:13 Elias is indeed come. See note on Matthew 17:12.