How do we know Elijah's prophecy is fulfilled?

The fulfillment of Elijah's prophecy is confirmed in the New Testament, specifically through the ministry of John the Baptist. In Matthew 11:13, Jesus states that 'all the prophets and the law prophesied until John,' indicating that John embodies the prophetic voice that preceded Christ. John the Baptist's message echoed Elijah's; it called for repentance and identified Jesus as the Messiah, the Lamb of God who takes away the sins of the world. This aligns with Malachi’s prophecy about Elijah, who would come before the 'great and dreadful day of the Lord.' Thus, we see that the prophetic function is not only qualified through lineage but is fulfilled in the spirit and mission to restore the proper worship of Yahweh and present Christ to the people.