The Purest Thing on Earth

What is the foulest thing on earth?
Think if you can and tell!
It is a soul by sin defiled,
'Tis only fit for Hell;
It is the loathsome earthly den
Where evil spirits dwell.
And what's the purest thing on earth?
Come, tell me, if you know!
'Tis that same soul by Jesus' blood
Washed whiter far than snow!
There's naught more pure above the sky,
And naught else pure below.