Unless the vessel be pure, everything which is poured into it will turn sour..

It's hardly in a body's pow'r,To keep, at times, frae being sour..

You noticed that I wore this outfit twice? Why, the only thing you wear twice is a sour expression..

Nothing is so sour that it can't be sweetened by a good attitude..

Ambition has its disappointments to sour us, but never the good fortune to satisfy us..