These Christians of Syria (1) once filled the whole region, yet all but a small handful entered Islam, so that within the Muslim community they are now like a single black hair on a white bull.
Likewise, the Zoroastrians were a nation whose numbers only Allah could reckon (2); they embraced Islam collectively, with only a negligible minority left behind. Their lands became Muslim territories, and those who did not accept Islam lived under jizya and humiliation (3).
In the same way, the majority of the Jews embraced Islam, and only a few scattered remnants remain dispersed across the lands.
Accordingly, the assertion of this ignorant man—“These two nations, whose numbers only Allah can know, have rejected Muhammad ﷺ”—is an obvious falsehood and a manifest slander. Even if every one of them had unanimously chosen unbelief, they would only be following the precedent of the people of Noah, among whom he lived for one thousand years less fifty, calling them to Allah and showing them signs that established the divine proof against them, yet they persisted in disbelief (4) except for a few (5), as the Most High says:
“And none believed with him except a few” (Hud 40).
Those people were many times more numerous than these two disbelieving nations—the people who incurred wrath and those who went astray.