Synaxis of the Holy Theotokos

Reading from the Synaxarion:

This Synaxis - which is to say, our coming together to glorify the
Theotokos - is celebrated especially in her honour because she gave birth
supernaturally to the Son and Word Of God, and thus became the instrument of the
salvation of mankind.

Kontakion in the Plagal of the Second Tone
He, who was begotten of the Father before the morning star, without a
mother, becomes incarnate of you today, without a father. Wherefore, a
star announces the good news to the Magi. Angels with shepherds praise
your immaculate birth-giving, O Full of Grace.