Other ways of saying it:
Three Bulls pastured for a long time together. A Lion lay in hiding, hoping to make them his prey, but he was afraid to attack them while they were with each other.
One by one, he lured them away from each other with whispered words.
"Better grass over here."
Having separated them with his sneaky speeches, he then attacked them without fear as they fed alone, then feasted on them one by one at his leisure.
Comment: Courtesy of Aesop (and not the AFL-CIO) The Lion and the Three Bulls is a fable with a timeless moral, though a rather dated telling.
Our children are meant to take the lesson "join with others," or "stick together for the best defense," but Aesop's telling of the story is from the Lion's point of view. (Contrast this with The Three Little Pigs, a story told from the point of view of prey, not predator.)
Because we don't hear from the bulls, and because they make the wrong choice, the fable is more warning than example. Since it's from the Lion's point of view, the message is really more "Divide and conquer" than "United We Stand, Divided We Fall."
Of course, there's nothing to keep a parent from giving the fable a "Three Little Pigs" treatment - just tell it from the point of view of the bulls hearing a voice in the long grass tempting them away from each other.
Of course, you still end up with dead bulls. If that's not a story you want to tell your child, then this probably isn't the fable for your purposes!
How to use Aesop's Fables.
More stories with morals.
Storytelling to improve behavior.