ירמיהו, פרק ח׳, פסוק כ״ג

Facing an approaching disaster and a nation that refuses to repent, the prophet realizes there is no longer any hope for healing. In this hopeless reality, his only remaining response is to surrender to deep grief over the tragedy [ביאור שטיינזלץ]. His feelings toward the people, however, are deeply conflicted. On one hand, his fierce love for them drives him to weep endlessly over their fate. On the other hand, their evil actions make him want to flee and distance himself from them entirely [מלבי״ם].

Driven by this profound sorrow, he expresses a desperate wish to mourn for the fallen without interruption [מצודת ציון, רד״ק]. He hopes that his head could turn entirely into water and his eyes into a continuous, flowing spring of tears [רד״ק, מצודת דוד, מצודת ציון]. This specific desire stems from a natural physical limitation. Prolonged weeping eventually dries out the mind until the tears simply run out. To overcome this, the prophet wishes his head could transform into a permanent source of water. This would constantly supply his eyes, allowing him to cry day and night without his tears ever stopping [מלבי״ם].