The law of prayer is the law of belief.

The title is an approximate translation of a very ancient aphorism of Catholic faith.
So, with the Church calendar being in Advent season and thinking of advent prayers it seems fitting to present an advent prayer that all of you are likely to know.

Prayer:

December 17, O Wisdom
O Come, Thou Wisdom from on high,
And order all things mightily
To us the path of knowledge show
And teach us in her ways to go.


December 18, O Lord and Ruler
O Come, O Come, Thou Lord of might:
Who to Thy tribes on Sinai's height
In Ancient times did give the law
In cloud, and majesty, and awe.


December 19, O Root of Jesse
O Come, thou rod of Jesse's stem,
From ev'ry foe deliver them
That trust Thy mighty power to save,
And give them victory o'er the grave.


December 20, O Key of David
O Come, thou Key of David, come,
And open wide our heav'nly home,
Make safe the way that leads on high,
That we no more have cause to sigh.


December 21, O Dawn of the East
O Come, Thou Dayspring from on High
And cheer us by Thy drawing nigh.
Disperse the gloomy clouds of night
And death's dark shadow put to flight.

Refrain

December 22, O King of the Gentiles
O Come, Desire of nations, bind
In one the hearts of all mankind.
Bid every strife and quarrel cease
And fill the world with heaven's peace.


December 23, O Emmanuel
O Come, O Come, Emmanuel,
And ransom captive Israel,
That mourns in lonely exile here
Until the Son of God appear.

Some ask about the source(s) of Holy Tradition.
Well, the source from which Holy Tradition flows is this:
From these two things sprang forth the canon of Holy Scripture.
From the canonical scriptures springs forth the words upon which the Church builds some of her theology
and the rest of her theology springs forth from her prayer life and her worship life.
This is as it ought to be for Christianity.