'Curb' in the Bible

Be ye not as a horse -- as a mule, Without understanding, With bridle and bit, its ornaments, to curb, Not to come near unto thee.

To the Overseer, to Jeduthun. -- A Psalm of David. I have said, 'I observe my ways, Against sinning with my tongue, I keep for my mouth a curb, while the wicked is before me.'