ירמיהו, פרק מ״ג, פסוק ט׳

Prophets of Israel were frequently directed to carry out physical, symbolic actions to make their messages tangible. There is a profound purpose behind these physical displays. Typically, a harsh prophecy can be reversed if the people repent and God withdraws His decree. However, once a prophet performs a physical action to represent the prophecy, the decree is cemented and becomes absolute [מלבי״ם].

In this instance, Jeremiah is instructed to take large stones and conceal them [מצודת ציון]. He is told to hide them near the entrance of Pharaoh's palace [מצודת דוד]. The exact method of concealment is understood in slightly different ways. One perspective suggests the focus is on the action of wrapping and covering the stones completely within mud or clay [רש״י]. The primary approach among commentators, however, is that the stones are buried in a specific building material, namely a thick mortar made of clay, sand, and lime used for construction in Egypt [מצודת ציון, מלבי״ם, רד״ק, ביאור שטיינזלץ].

The burial takes place at the local brickworks. This location is either the kiln area where bricks are manufactured and fired [מצודת דוד, מצודת ציון, רד״ק], or directly inside the molds used to cast the bricks themselves [ביאור שטיינזלץ]. Crucially, this striking act at the threshold of the Egyptian ruler's home is not done in secret. It is performed publicly, in the full view of the Judeans who are staying in the area [ביאור שטיינזלץ].