Halliwell suggests that the two last lines were imitated from the following in Bishop Ken's Evening Hymn:
Let my blest guardian, while I sleep,
His watchful station near me keep.
But if there was any imitation in the case, it was the bishop who copied from the folk-rhymer, not the folk-rhymer from the bishop.
The thought of the coming of death in sleep, is expressed in a prayer that may be sometimes seen inscribed at the head and foot of the bed in Norwegian homesteads:
HEAD.
Here is my bed and sleeping place;
God, let me sleep in peace
And blithe open my eyes