A clam came out to bask in the sun, and a snipe flew to peck at its meat. The clam immediately closed and clamped the snipe's mouth. The snipe said, "If it doesn't rain today, if it doesn't rain tomorrow, you will die." The mussel said to the snipe, "If you can't open your mouth today, you will starve to death tomorrow." Neither snipe nor clam will give up on each other. Then a fisherman came and caught them both together.
This is a story in which the two sides are at loggerheads and the third party benefits from it. Later, it evolved into an idiom: the snipe and the clam compete, and the fisherman gains.
An idiom with a similar meaning to "when the snipe and the clam compete, the fisherman gains" is "when two tigers compete, there must be a wound"; The idiom with the opposite meaning to "the snipe and the clam compete, the fisherman gains" is "help each other in the same boat, be of one mind and one mind"