John Mason Neale's translation of Venantius Fortunatus' Passiontide hymn Pange Lingua Gloriosi Proelium Certaminis. The full version here is very seldom used, and Percy Dearmer and others have produced variations on some verses. The plainsong chant 'Pange Lingua' and the hymn-tunes Picardy and Grafton may be used for this hymn, as for Of the Glorious Body Telling and Let All Mortal Flesh Keep Silence.

Sing, my tongue, the glorious battle
Sing the last, the dread affray;
O'er the Cross, the victor's trophy,
Sound the high triumphal lay:
Tell how Christ, the world's Redeemer,
As a victim won the day.

God, His Maker, sorely grieving
That the first-made Adam fell,
When he ate the fruit of sorrow,
Whose reward was death and hell,
Noted then this Wood, the ruin
Of the ancient wood to quell.

For the work of our salvation
Needs would have his order so,
And the multiform deceiver's
Art by art would overthrow,
And from thence would bring the med'cine
Whence the insult of the foe.

Wherefore, when the sacred fulness
Of the appointed time was come,
This world's Maker left His Father,
Sent the heav'nly mansion from,
And proceeded, God Incarnate,
Of the Virgin's holy womb.

Weeps the Infant in the manger
That in Bethlehem's stable stands;
And His limbs the Virgin Mother
Doth compose in swaddling bands,
Meetly thus in linen folding
Of her God the feet and hands.

Thirty years among us dwelling,
His appointed time fulfilled,
Born for this, He meets His Passion,
For this that He freely willed:
On the Cross the Lamb is lifted,
Where His life-blood shall be spilled.

He endured the nails, the spitting,
Vinegar, and spear, and reed;
From that holy Body broken
Blood and water forth proceed:
Earth, and stars, and sky, and ocean,
By that flood from stain are free.

Faithful Cross! above all other,
One and only noble Tree!
None in foliage, none in blossom,
None in fruit thy peer may be;
Sweetest Wood and sweetest Iron!
Sweetest Weight is hung on thee.1

Bend thy boughs, O Tree of glory!
Thy relaxing sinews bend;
For awhile the ancient rigor,
That thy birth bestowed, suspend;
And the King of heavenly beauty
On thy bosom gently tend!

Thou alone wast counted worthy
This world's ransom to uphold;
For a shipwrecked race preparing
Harbour, like the Ark of old;
With the sacred Blood anointed
From the smitten lamb that rolled.

To the Trinity be glory
Everlasting, as is meet;
Equal to the Father, equal
To the Son, and Paraclete:
Trinal Unity, whose praises
All created things repeat.

1: I recall that one source (Hymns Ancient and Modern, probably) has these two lines at the end of this verse:

Sweet the wood, and sweet the iron
And thy load, most sweet is He.

Everything Hymnal