John Calvin Commentary Romans 3:14

"Whose mouth is full of cursing and bitterness:" — Romans 3:14 (ASV)

Then he says that their mouth is full of cursing and bitterness—a vice of an opposite character to the former. But the meaning is that they are in every way full of wickedness, for if they speak smoothly, they deceive and blend poison with their flatteries; but if they draw forth what they have in their hearts, bitterness and cursing stream out.