Numbers 35:33

Defile not. To inspire a greater horror for murder the earth was represented as defiled by blood, and only to be purified by the death of the criminal. Without shedding of blood, there is no remission, Hebrews ix. 22. (Haydock) --- On the same principle, our churches, &c., are deemed profane when murder, or some great indecencies, have been committed in them, so that they require a fresh consecration. (Calmet)