Allaah commanded Jibreel to blow through the neck of Maryams garment, and this breath went down and by the will of Allaah entered her womb, so it became a soul that Allaah had created. Allaah has explained how He created Eesaa (peace be upon him), as He said (interpretation of the meaning):

And she who guarded her chastity [Virgin Maryam (Mary)], We breathed into (the sleeves of) her (shirt or garment) [through Our Rooh Jibreel (Gabriel)] [al-Anbiya