It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Every human being, his mother gives birth to him upon the fitrah (natural disposition); his parents make him a Jew, a Christian or a Magian. If they are both Muslims, then he is a Muslim too. Every human being, when his mother gives birth to him, Satan pokes him in his sides, except Maryam and her son."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12142