How u say tell him to cut beef in spanish?

(Literally) 'di(ga)le que corte la carne de vaca'

But it depends on what you mean by 'cut beef' - 'stop complaining/talking'?

'Di(ga)le que cesa de quejarse' = tell him to stop complaining

'Di(ga)le que cesa de charlar' = tell him to stop prattling