Blud

Fairie Queene, Book II: Canto ii. Sir Guyon and his Palmer have discovered a dead knight and his dying lady, a knife in this latter's breast. But the couple's baby is in his mother's arms, and playing boyishly in the stream of blood. Ugh. Anyhow, the mother dies, and Guyon tries to wash the baby's hands -- but the stream nearby is a magic stream that, for odd reasons, will accept no taint and is therefore no good for washing.

Then soft himselfe inclyning on his knee
Downe to that well, did in the water weene
(So loue does loath disdainfull nicitee)
His guiltie hands from bloudie gore to cleene,
He washt them oft and oft, yet nought they beene
For all his washing cleaner. Still he stroue,
Yet still the litle hands were bloudie seene;
The which him into great amaz'ment droue,
And into diuerse doubt his wauering wonder cloue.

I feel confident in suggesting: Shakespeare clearly read this passage, and it was in his mind when he wrote Lady Macbeth.