In Matthew 8, Pastor Armstrong discusses how Jesus healing the leper was considered to be a miracle only capable by the Messiah. But in the Old Testament (2 Kings 5:10), we read of Elisha giving instruction for Naman to wash himself in the Jordan River and thus be healed of leprosy. So as Jesus was not the first to heal a leper how can the story in Matthew be considered a Messianic miracle?
As Pastor Armstrong explains in the teaching, the book of Leviticus contains an entire chapter (Leviticus 14) devoted to how a Jew healed of leprosy must respond to the healing. After centuries, the rabbis noticed that the rituals required by Levitcus 14 had never been used in all the history of Israel, because no Jew had ever been healed of leprosy. This caused the rabbis to assume (correctly) that this miracle could only be done by the Messiah when He arrived. So the healing of a leper was a mark of the Messiah.
Naaman, the General, was not a Jew (he was Syrian), so he was not under the Law of Israel and therefore he was not required to follow the rituals found in Leviticus 14 after being healed. So his healing (though a miracle) did not serve as a Messianic Miracle because it never involved Leviticus 14.
So the Messianic miracle was not healing anyone of leprosy. It was healing a Jew of leprosy, because that was the only way for Leviticus 14 to apply. Jesus Himself testifies that no Jew was ever healed of leprosy by the prophet:
Finally, Jesus affirms that healing a leper was proof He was the Messiah when he answers John's disciples in Luke:
For more information on the Messianic Miracles, please read: What is the unforgiveable sin?