John Wesley on Joshua 20:3

Unwittingly - Heb. Through ignorance, or error, or mistake, and without knowledge. The same thing twice repeated to cut off all the expectations that wilful murderers might have of protection here; God having declared, that such should be taken even from his altar, that they might be killed. It is strange that any Christians should make their sanctuaries give protection to such persons whom God hath so expressly excepted from it! Avenger - The nearest kinsman, who had right or power to demand, or take vengeance of the slaughter.