Feast of the The Circumcision of Christ & the Eighth Day of Christmas

From the 13th century until the Calendar reform by Pope John XXIII in 1960, today was the Feast of the Circumcision of Christ. With John's reforms, it became simply the Octave Day of Christmas.

In the post-Conciliar Calendar of Paul VI, it was renamed the Solemnity of Mary, Mother of God. Through all the changes tho', the Gospel has remained that of the Circumcision,

Luke 2:21At that time, when eight days were fulfilled for the circumcision of the Child, His name was called Jesus, the name given Him by the angel before He was conceived in the womb. 

However, in the Mass of Paul VI it has been augmented with verses 16-20,  

  16 And they came with haste; and they found Mary and Joseph, and the infant lying in the manger.17 And seeing, they understood of the word that had been spoken to them concerning this child.18 And all that heard, wondered; and at those things that were told them by the shepherds.19 But Mary kept all these words, pondering them in her heart.20 And the shepherds returned, glorifying and praising God, for all the things they had heard and seen, as it was told unto them.

Circumcision of Christ,
Menologion of Basil II, 979-984

The Circumcision, by Luca Signorelli

The Homily from Matins of the Feast

Homily by St. Ambrose, Bishop of Milan.
Book ii on Luke ii
So the Child is circumcised. This is the Child of Whom it is said: Unto us a Child is born, unto us a Son is given, Isa. ix. 6. Made under the law to redeem them that were under the law. Gal. iv. 4. To present Him to the Lord, 22. In my Commentary on Isaiah I have already explained what is meant by being presented to the Lord in Jerusalem, and therefore I will not enter into the subject again. He that is circumcised in heart gaineth the protection of God, for the eyes of the Lord are upon the righteous. Ps. xxxiii. 16. Ye will see that as all the ceremonies of the old law were types of realities in the new, so the circumcision of the body signified the cleansing of the heart from the guilt of sin. 

But since the body and mind of man remain yet infected with a proneness' to sin, the circumcision of the eighth day is also a type of that complete cleansing from sin which we shall have at the resurrection. This ceremony was also performed in obedience to the commandment of God: Every male that openeth the womb shall be called holy unto the Lord. These words were written with especial reference to the delivery of the Blessed Virgin. Truly He That opened her womb was holy, for He was altogether without spot, and we may gather that the law was written specially for Him from the words of the Angel: That Holy Thing Which shall be born of thee, shall be called the Son of God.

Among all that are born of women the Lord Jesus Christ stood alone in holiness. Fresh from His immaculate Birth, He felt no contagion from human corruption, and His heavenly Majesty drove it away. If we are to follow the letter and say that every male that openeth the womb is holy, how shall we explain that so many have been unrighteous? Was Ahab holy? Were the false prophets holy? Were they holy on whom Elijah justly called down fire from heaven? But He to Whom the sacred commandment of the law of God is mystically directed is the Holy One of Israel; Who also alone hath opened the secret womb of His holy Virgin-bride the Church, filling her with a sinless fruitfulness to give birth to Christian souls.

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Under the normal conditions, one may receive a plenary indulgence for reciting the Veni, Creator Spiritus on the first day of the year:

Creator-Spirit, all-divine,
Come, visit every soul of thine,
And fill with thy celestial flame
The hearts which thou thyself didst frame.

O gift of God, thine is the sweet
Consoling name of Paraclete
And spring of life and fire and love
And unction flowing from above.

The mystic sevenfold gifts are thine,
Finger of God's right hand divine;
The Father's promise sent to teach
The tongue a rich and heavenly speech.

Kindle with fire brought from above
Each sense, and fill our hearts with love;
And grant our flesh, so weak and frail,
The strength of thine which cannot fail.

Drive far away our deadly foe,
And grant us thy true peace to know;
So we, led by thy guidance still,
May safely pass through every ill.

To us, through thee, the grace be shown
To know the Father and the Son;
And Spirit of them both, may we
Forever rest our faith in thee.

To Sire and Son be praises meet,
And to the Holy Paraclete;
And may Christ send us from above
That Holy Spirit's gift of love.
Amen

And it's the Eighth Day of Christmas.

On the eighth day of Christmas, my true love sent to me

8 maids a-milking.