The use of the mill in the eastern world was very ancient, and peformed by the lowest of the people, So that when describing the different ranks whom the Lord would destroy in the general destruction of the firstborn in Egypt, the phrase is, "from the first-born of Pharoah that sitteth upon his throne, even unto the first born of the maid servant that is behind the mill." (Exodus 11:5) Hence when the Philistines had put out Samson's eyes, they bound him in fetters of brass, and compelled him "to grind in the prison-house." (See Judges 16:21)
There is a very gracious precept in the law of Moses on the subject of grinding, which serves to shew the Lord's tender compassion over his people. "No man shall take the nether or the upper millstone to pledge, for he taketh a man's life to pledge." (Deuteronomy 24:6) In what a very sweet and engaging point of view doth this represent the Lord! And when the precept is heightened in relation to spiritual bread, with what affection may the poor look unto Jesus, the bread of life, concerning it!