Charles Ellicott Commentary Joshua 5:2

"At that time Jehovah said unto Joshua, Make thee knives of flint, and circumcise again the children of Israel the second time." — Joshua 5:2 (ASV)

THE CIRCUMCISION OF ISRAEL BY JOSHUA (Joshua 5:2–9).

Make you sharp knives. —Authorities are divided between the rendering “sharp knives” and “knives of flint.” The first seems best supported, as far as the meaning of the words is concerned. The expression is “knives of tsurim.” The word tsûr does not seem anywhere to be connected with the material of the tool, but rather with the edge of it. Knives of keen edge is, therefore, the better translation. At the same time they may have been stone knives in this instance.

The idea that they were so is supported by an addition in the Septuagint to Joshua 24:30: “They put with him (Joshua) into the tomb ... the knives of stone with which he circumcised the children of Israel ... and there they are to this day.” The ceremony being a kind of special consecration, it is not unlikely to have been performed with special instruments, which were not used before or after. Compare Psalm 89:43, “You have turned the tsûr (keen edge) of his sword”; 2 Samuel 2:16, “Helkath Hazzurim”—that is, the field of keen blades; Exodus 4:25, “Zipporah took a tzôr”; Ezekiel 3:9, “an adamant harder than tzôr.”