A device designed to cover an animal’s mouth and prevent it from biting or eating.

Cattle were often used in ancient Palestine when a large quantity of grain was to be threshed. In preparation, the sheaves were untied and distributed over the hard-packed surface of the threshing floor until a thick layer was formed. Then one or more animals trod the grain with their hooves or it was threshed by means of a threshing sledge or other implement they drew over it. The Mosaic Law commanded: “You must not muzzle a bull while it is threshing.” (De 25:4) Thus it was not tortured with a desire to eat some of the grain that it was expending its strength to thresh.​—Compare Pr 12:10.

The principle involved at Deuteronomy 25:4 can also be applied to human laborers. Paul told Timothy: “Let the older men who preside in a fine way be reckoned worthy of double honor, especially those who work hard in speaking and teaching.” Then, confirming his counsel, the apostle quoted the law about not muzzling a bull when it  is threshing grain. (1Ti 5:17, 18) Also, as part of Paul’s reasoning to show the Corinthians that “the Lord ordained for those proclaiming the good news to live by means of the good news,” he quoted Deuteronomy 25:4 and then wrote: “Is it bulls God is caring for? Or is it altogether for our sakes he says it? Really for our sakes it was written, because the man who plows ought to plow in hope and the man who threshes ought to do so in hope of being a partaker.”​—1Co 9:8-14.

The psalmist David used “muzzle” figuratively when he said that he set one as a guard to his mouth to keep from sinning.​—Ps 39:1.