E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
He took bread and salt, i.e. he took his oath. Bread and salt were formerly eaten when an oath was taken.
Cast thy bread upon the waters: for thou shalt find it after many days (Eccles. xi. 1). When the Nile overflows its banks the weeds perish and the soil is disintegrated. The rice-seed being cast into the water takes root, and is found in due time growing in healthful vigour.
Dont quarrel with your bread and butter. Dont foolishly give up the pursuit by which you earn your living.
To know which side ones bread is buttered. To be mindful of ones own interest.
To take the bread out of ones mouth. To forestall another; to say something which another was on the point of saying; to take away anothers livelihood. (See under BUTTER.)