The birth of Jesus or the birth of Christians?

"John 1:13 is a crucial point for the textual citicism of the New Testament. This verse, in fact, admits to two readings, a plural and the singular. The plural refers to Christians ... the singular to Christ. ... The author proceeds to examine the doctrinal implications of the singular reading. These he divides in two; first Christological and then (in the second instance, almost as a reflex) Mariological. The Christological aspect is obviously primary, given that the verse speaks of the Incarnation. The Evangelist John bears witness also to the virginal conception of Jesus in Mary's womb. ... The virginity of Mary, in all its aspects, is a consequence of the divine nature of the Son"--Foreword.