The pagan are guilty of but one sin - idolatry; the covenant-people commit two - they abandon the true God; they serve idols.
Fountain - Not a spring or natural fountain, but a tank or reservoir dug in the ground (see Jeremiah 6:7), and chiefly intended for storing living waters, i. e., those of springs and rivulets. The cistern was used for storing up rain-water only, and therefore the quantity it contained was limited.