This text comes from A First Series of Hymns and Songs, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
The heathen monarch sits enthron'd
In all his pomp and pride,
With twice ten thousand men at arms
Assembled at his side.
He greets the band of holy men
Who march in pain and toil,
To plant the banner of the Cross
In Britain's sea-girt isle.
Not in the strength of man they come,
No human arms they bear;
Their armour is the shield of faith,
Their weapons fast and prayer.
To Faith's good fight in holy trust,
In courage calm and high,
Their fearless leader guides them on,
To conquer or to die.
They come, and soon the heathen gods
Before them prostrate fall,
As erst of old to trumpet's clang
Fell down a city's wall.
O blessed day, whose light illumes
The present and the past;
Thy fire of faith must still burn on,
As long as time shall last:—
Though faint and feeble now perchance,
Yet still a deathless flame;
And ages yet unborn shall learn
To bless Augustine's name.