From Longman Dictionary of Contemporary Englishthe sweat of somebody’s browthe sweat of somebody’s browliteraryWORK HARD the hard effort that someone has made in their work → sweat
Examples from the Corpus
the sweat of somebody’s brow• Bread is a symbol of our work, because of the bread we earn by the sweat of our brow.• No need to toil in the sweat of one's brow to support it! 