‘When I see blood I will pass over you in the night’

Noltland Castle on Westray is 16th Century. Surrounding it are 17th Century additions, one of which has this fragile arch still remaining. A faint carving nearby says ‘When I see blood I will pass over you in the night’. I wonder if anyone daubs the gatepost with the fresh blood of a newly slaughtered spring lamb in order that God will pass over the Castle and not kill all the newborn children, like they did in the tenth plague of Egypt in the Book of Exodus. The Passover? I’ll pass thank you.