This verse is joined in the Hebrew to the preceding chapter. But any break at all here interrupts the meaning.
A fountain - Rather, “a reservoir,” in which tears had been stored up, so that the prophet might weep abundantly.
Related Commentaries of Jeremiah 9:1
Jeremiah 9:1
1 Oh that my head were waters, and mine eyes a fountain of tears, that I might weep day and night for the slain of the daughter of my people!