Question: "How old was Mary when Jesus was born?"
Answer: While the Bible does not specifically state how old Mary was when Jesus was born, most Christian historians speculate that she was around 15—16 years of age at the time of Jesus’ birth. According to Jewish customs at the time, a young woman might become betrothed to a young man as early as 12 years of age, though the consummation of their marriage through ceremony and physical intimacy would not happen until they were legally married, many months or even years later.
In Luke 1:39–56, we learn that Mary traveled from Galilee to Judah to visit her relative Elizabeth. She would have had to cross a great distance though the territory of Samaria. We do not know if she traveled alone, with servants, or in the company of other family members. However, there is a great likelihood that, even with adult escorts, Mary would have needed to be both physically and emotionally mature enough to handle such a journey.
No matter what Mary’s age when Jesus was born, her spiritual maturity is indeed evident. The mother of Jesus is described by God as “highly favored” (Luke 1:28). When presented with the news that she would conceive the holy Son of God, Mary responds with pure faith and obedience by saying, “Behold, I am the servant of the Lord; let it be to me according to your word” (Luke 1:35–38). Her song (Luke 1:46–55) is full of Scripture—by some counts, there are 10 quotations of and allusions to the Old Testament in the Magnificat—another strong proof of Mary’s learning and spiritual maturity.