The initial idioms of the letter B

be back in business	be back in harness
be back on the rails	be backed into a corner
be backward in coming forward	be bad news
be bag	be bang on
be banging head against a brick wall	be barking mad
be barking up the wrong tree	be batting a thousand
be baying for blood	be beat
be before (one's) time	be before time
be behind	be behind the eight ball
be below the belt	be beside
be beside (oneself)	be beside the point
be better off dead	be beyond ken
be beyond (one's) ken	be beyond the pale
be big of	be big of (one)
be big on	be larger than life