In the name of our God we will set up our banners.@Psalm 20:5
John M. Neale (1818–1866)

Venantius Fortunatus, 569 (Vexilla Regis prodeunt); translated from Latin to English by John M. Neale, Mediaeval Hymns and Sequences, 1851. Legend says that on November 19, 568, St. Radegund presented to the town of Poitiers a fragment believed to be the true Cross. Fortunatus was the one chosen to receive the relic on its arrival at Poitiers. When the bearers of the holy fragment were two miles distant from the town, Fortunatus, with a great gathering of believers and enthusiasts, some carrying banners, crosses and other sacred emblems, went forth to meet them. As the marched, they sang this hymn, which Fortunatus had written.

Hamburg Lowell Mason, 1824; first appeared in The Boston Handel and Haydn Society Collection of Church Music, third edition, 1825 (πŸ”Š pdf nwc).

Lowell Mason (1792–1872)

The royal banners forward go,
The cross shines forth in mystic glow;
Where He in flesh, our flesh who made,
Our sentence bore, our ransom paid.

Where deep for us the spear was dyed,
Life’s torrent rushing from His side,
To wash us in that precious flood,
Where mingled water flowed, and blood.

Fulfilled is all that David told
In true prophetic song of old,
Amidst the nations, God, saith he,
Hath reigned and triumphed from the tree.

O tree of beauty, tree of light!
O tree with royal purple dight!
Elect on whose triumphal breast
Those holy limbs should find their rest.

Blest tree, whose chosen branches bore
The wealth that did the world restore,
The price of humankind to pay,
And spoil the spoiler of his prey.

Upon its arms, like balance true,
He weighed the price for sinners due,
The price which none but He could pay,
And spoiled the spoiler of his prey.

O cross, our one reliance, hail!
Still may thy power with us avail
To give new virtue to the saint,
And pardon to the penitent.

To Thee, eternal Three in One,
Let homage meet by all be done:
As by the cross Thou dost restore,
So rule and guide us evermore.