According to Luke, God revealed this information to a Jewish prophet named Simeon:
Now there was a man in Jerusalem whose name was Simeon; this man was righteous and devout, looking forward to the consolation of Israel, and the Holy Spirit rested on him. It had been revealed to him by the Holy Spirit that he would not see death before he had seen the Lord’s Messiah.
Guided by the Spirit, Simeon came into the temple; and when the parents brought in the child Jesus, to do for him what was customary under the law, Simeon took him in his arms and praised God, saying,
“Master, now you are dismissing your servant in peace, according to your word;
for my eyes have seen your salvation,
which you have prepared in the presence of all peoples,
a light for revelation to the Gentiles
and for glory to your people Israel.”
And the child’s father and mother were amazed at what was being said about him. Then Simeon blessed them and said to his mother Mary, “This child is destined for the falling and the rising of many in Israel, and to be a sign that will be opposed so that the inner thoughts of many will be revealed—and a sword will pierce your own soul too.” (Luke 2:25-34, NRSV)
Merry Christmas! Like Simeon, let us thank God for sending his Messiah!