Today the young maidens come forth joyfully, carrying their lamps before the super-sensuous torch, and in a noble manner take her into the Holy of Holies, going before and foretelling the ineffable Ray which shall shine forth from her, lighting in the spirit those who sit in the darkness of folly.
--Vespers of the Feast
As we celebrate the Feast of the Entrance of the Theotokos  into the Temple, we offer a hymn of praise to her who became a living temple of God. But this feast is also a prelude to the Feast of the Nativity. It is here that we are ushered fully into the Nativity season. As the Troparion of the Feast proclaims, "Today is the prelude of God's goodwill". It is now, during Orthros for the Feast of the Entrance, that we first hear the joyous words of the Nativity Canon: "Christ is born, glorify Him. Christ is come from heaven, receive ye him. Christ is on earth, be ye elevated." In the words of Fr. Alexander Schmemann :
With these words something changes in our life, in the very air we breathe, in the entire mood of the Church’s life. It is as if we perceive far, far away, the first light of the greatest possible joy — the coming of God into His world! Thus the Church announces the coming of Christ, the Incarnation of God, His entrance into the world for its salvation.
Thus we continue our time of fasting and preparation in joyous knowledge of what awaits: the uncontainable God, born in the cave of the Virgin for the salvation of mankind.
Zachariah cried in gladness, I open to thee the gate of Temple, O gate of the Lord. Abide therein rejoicing; for I have known and do believe that the salvation of Israel shall come now openly, and from thee shall be born the Word of God Who granteth the world the Great Mercy.
--from the Aposticha, Vespers of the Feast
I behold a strange and wonderful mystery: the cave a heaven, the Virgin a cherubic throne, and the manger a noble place in which hath laid Christ the uncontained God. Let us, therefore, praise and magnify Him.
--Nativity Canon, Ode 9