Read Luke 2:22-40
22 The time came for Joseph and Mary to perform the ceremony of purification, as the Law of Moses commanded. So they took the child to Jerusalem to present him to the Lord, 23as it is written in the law of the Lord: “Every firstborn male is to be dedicated to the Lord.” 24They also went to offer a sacrifice of a pair of doves or two young pigeons, as required by the law of the Lord.
25 At that time there was a man named Simeon living in Jerusalem. He was a good, God-fearing man and was waiting for Israel to be saved. The Holy Spirit was with him 26and had assured him that he would not die before he had seen the Lord’s promised Messiah. 27Led by the Spirit, Simeon went into the Temple. When the parents brought the child Jesus into the Temple to do for him what the Law required, 28Simeon took the child in his arms and gave thanks to God:
29 “Now, Lord, you have kept your promise,
and you may let your servant go in peace.
30 With my own eyes I have seen your salvation,
31 which you have prepared in the presence of all peoples:
32 A light to reveal your will to the Gentiles
and bring glory to your people Israel.”
33 The child’s father and mother were amazed at the things Simeon said about him. 34Simeon blessed them and said to Mary, his mother, “This child is chosen by God for the destruction and the salvation of many in Israel. He will be a sign from God which many people will speak against 35and so reveal their secret thoughts. And sorrow, like a sharp sword, will break your own heart.”
36–37 There was a very old prophet, a widow named Anna, daughter of Phanuel of the tribe of Asher. She had been married for only seven years and was now 84 years old.b She never left the Temple; day and night she worshipped God, fasting and praying. 38That very same hour she arrived and gave thanks to God and spoke about the child to all who were waiting for God to set Jerusalem free.
39 When Joseph and Mary had finished doing all that was required by the law of the Lord, they returned to their home town of Nazareth in Galilee. 40The child grew and became strong; he was full of wisdom, and God’s blessings were upon him.
"Now Lord, you have kept your promise and you may let your servant go in peace."
The birth of Jesus is enough for Simeon to know that God's Kingdom will come.