The Plymouth Brethren affirm Isaiah 7:14 as a messianic prophecy explicitly fulfilled in the virgin birth of Jesus Christ. While the Hebrew term alma can be debated in secular scholarship, the Brethren follow the traditional Christian reading—affirmed by the Septuagint (parthenos) and Matthew's explicit quotation—that the prophet foretold a miraculous conception. This interpretation bridges Old Testament prediction with New Testament fulfillment and stands as a cornerstone of evangelical Christology.

Brethren writers and preachers emphasized the historical and doctrinal significance of the virgin birth as a sign of Christ's unique incarnation—neither entirely human nor a mere divine appearance, but God himself taking on true humanity. J.N. Darby and other Brethren scholars interpreted Isaiah's sign within the larger framework of God's sovereign plan for redemption, not merely as a wonder but as a theological marker of Christ's divine origin and sinlessness. The doctrine strengthens confidence in Christ's person and work as the promised Messiah.