I sang this to my daughter for years. We have just been discussing it. My version is as follows:

Sleep my little one, sleep
Fond virgil I keep.
Lay warm in thy bed
?? Not sure but probably 'Angels singing round thy head'

When the dawn tints the sky
God will bid thee arise
When the dawn tints the sky
God will bid thee arise.

Holy angels abide
All night by thy side
In dreams they unfold
Heaven's portals of gold

Slumber softly and rest
In thy dreamland so blest
Slumber softly and rest
In thy dreamland so blest