Yehezkiel 21:11-12

21:11 “‘He gave it to be polished,

to be grasped in the hand –

the sword is sharpened, it is polished –

giving it into the hand of the executioner.

21:12 Cry out and moan, son of man,

for it is wielded against my people;

against all the princes of Israel.

They are delivered up to the sword, along with my people.

Therefore, strike your thigh. ¹ 

[21:12]  ¹ sn This physical action was part of an expression of grief. Cp. Jer. 31:19.