Rabbi Singer gives the impression that Matthew was deliberately trying to mislead his readers. This is unlikely. Matthew was probably quoting from the Septuagint — a translation of the Hebrew Bible into Greek completed around the 2nd century BCE. The Septuagint translated ?????????????????? (ha’almah) as parthenos — meaning “virgin”.
Since the Septuagint predates Christianity, there’s no reason to think that the translators intentionally changed the meaning. Rashi, the famous Jewish commentator, stated that some Jews understood the verse as prophecy about a virgin birth: