This is an old song, often called a lullaby. There must be several versions, some African-American. Here is one:

ANGELS WATCHING OVER ME

All night, all day, angels watching over me, my Lord,
All night, all day, angels watching over me.

Sun is a-setting in the west, angels watching over me, my Lord,
Sleep my child, take your rest; angels watching over me.

All night, all day, angels watching over me, my Lord,
All night, all day, angels watching over me.
Angels watching

ANGELS WATCHING OVER ME
From the Wolf Collection, sung by 'unknown', audio.

... my lord,
All night, all day,
Angels watching over me.

Now I lay me down to sleep, oh, lordy,
Angels watching over me, my lord.
Pray the lord my soul to keep,
Angels watching over me.


Chorus:
All night, all day, oh, lordy,
Angels watching over me, my lord.
All night, all day,
Angels watching over me.

If I die before I wake, oh, lordy,
Angels watching over me, my lord.
Pray the lord my soul to take,
Angels watching over me.

Chorus:

If I live another day,
Angels watching over me, my lord,
Pray the lord will guide my way,
Angels watching over me.

John Quincy Wolf Folklore Collection.
Angels watching