The Virgin Birth (more precisely, the virginal conception) is attested in a number of ways in Matthew and Luke:-
(1) The sharp contrast between the long series of verses that use “begot” and the statement that Joseph was “the husband of Mary, of whom Jesus was born” (Mt. 1:16) clearly implies that a man was not involved in the procreation of Jesus.
(2) Mt. 1:18 states, “Before they came together she was found to be with child of the Holy Spirit.”
(3) Joseph’s desire to divorce her quietly presupposes that he had had no sexual relations with her (Mt. 1:19).
(4) The angel said “That which is conceived in her is of the Holy Spirit” (Mt. 1:20).
(5) In citing Isa. 7:14, Matthew called Mary a virgin (Mt 1:23).
(6) Joseph “knew her not until she had borne a son” (Mt. 1:25).
(7) Twice Luke called her a virgin and said that she was betrothed, which, although almost tantamount to marriage, was not marriage in the fullest sense (Lk 1:27).
(8) Mary was amazed at the angel’s announcement that she would conceive, since, as she said, “I know not a man” (Lk. 1:34, ASV).
(9) Luke said delicately but explicitly that the Holy Spirit, and not Joseph, would be the cause of the conception (Lk 1:35).
G.W. Bromiley, in ISBE (revised ed.), art. ‘Mary’