Exodus 11:5

⁵ and all the firstbornfirstborn in the landland of EgyptEgypt shall diedie, from the firstbornfirstborn of PharaohPharaoh who sitssits on his thronethrone, even to the firstbornfirstborn of the female servant who is behindbehind the millmill; and all the firstbornfirstborn of livestock.