John Calvin Commentary James 3:11

"Doth the fountain send forth from the same opening sweet [water] and bitter?" — James 3:11 (ASV)

Doth a fountain. He presents these comparisons to show that a cursing tongue is something monstrous, contrary to all nature, and subverts the order everywhere established by God. For God has so arranged things that are contrary, that inanimate things ought to deter us from a chaotic mixture, such as is found in a double tongue.