More Christmas Carol Lyrics: Flit Not

I've now sung this twice in Britten's "A Ceremony of Carols." I wonder how it sounded originally, and how 16th century folks would have felt when they heard it? The last two lines are so cool: If thou wikt foil thy foes with joy, then flit not from this heavenly Boy.

The incarnation is so much about contrasts, and this song lists so many of them.

This little Baby so few days old,
Is come to rifle Satan's fold;
All hell doth at his presence quake,
Though he himself for cold do shake;
For in this weak unarmèd wise
The gates of hell he will surprise.

With tears he fights and wins the field,
His naked breast stands for a shield;
His battring shot are babish cries,
His arrows looks of weeping eyes,
His martial ensings Cold and Need;
And feeble Flesh his warior's steed.

His camp is pitchèd in a stall,
His bulwark but a broken wall;
The crib his trench, haystalks his stakes;
Of shepherds he his muster makes;
And thus, as sure his foe to wound,
The angels' trumps alarum sound.

My soul, with Christ join thou in fight;
Stick to the tents that he hath pight.
Wothin his crib is surest ward;
This little Babe will be thy guard.
If thou wikt foil thy foes with joy,
then flit not from this heavenly Boy.