Exodus 11:5

That sitteth upon his throne; either now actually ruling with his father, as Solomon did even whilst David lived, 1 Kings 1:34; or, more probably, he that is to sit, the present time for the future, he whose right this is by the custom of Egypt, and by the law of nations. The first-born of the maid-servant; the poor captive slave that was in the prison, as it is Exodus 12:29, and there did grind at the mill. In those times and places they had divers mills, which were not turned about by wind or water, as ours are, but by the hands of their servants, who for that purpose stood behind the mill, and so with hard labour turned it about. See Judges 16:21 Isaiah 47:1,2 La 5:13.