There is no exactly corresponding passage, but the quotation harmonizes with the general tenor of several passages, as Isa 55:1; Isa 58:11; Zec 13:1; Zec 14:8; Eze 47:1; Joe 3:18.
Belly (κοιλιÌας)
The word is often used in the Old Testament for the innermost part of a man, the soul or heart. See Job 15:35; Job 32:19; Pro 18:8; Pro 20:27, Pro 20:30. The rite of drawing and pouring out the water pointed back to the smitten rock in the desert. In Exo 17:6, “there shall come water out of it,†is literally, “there shall come water from within him.†The word belly here means the inmost heart of the believer, which pours forth spiritual refreshment. Compare 1Co 10:4; Joh 4:14.