The source is a proverb: When someone steals a donkey, he pulls out the pegs.
pegs, short stakes. When someone stole the donkey, he went to pull the short stake that tied the donkey. Refers to others doing bad things, ending up unconsciously, and being regarded as a scapegoat for bad people. He is not the principal offender, but unintentionally participated in the crime, which belongs to the fault of "others steal donkeys and he pulls the pegs" and should not be punished too severely.
Allusion:
There is a joke about two thieves who both want to steal a farmer's donkey.
As a result, one of the thieves took the lead, untied the reins from the pegs where the donkey was tied, and stole the donkey. When another thief came and saw that the donkey was missing, he began to pull the wedge into the underground pegs according to the thief logic of "thieves enter the room empty-handed".
but before he succeeded, he was caught by farmers and wanted to turn him over to the government for stealing donkeys. Seeing this scene, the thief had a hard time arguing, so he had to admit it, obediently accompanied the farmer's donkey, and was ridiculed by everyone.
From then on, the joke "people took the donkey away and he pulled the pegs behind him" came into being. It is intended to remind some ignorant and stupid people not to make low-level and simple similar mistakes, not to mention adding mistakes to mistakes.
Extended information:
In the mid-199s, there was a movie "Days of Leaving Lei Feng", in which the protagonist Qiao Anshan was a typical example.
Qiao Anshan rescued the old man Liang who was injured by a car while driving. Because the old man's children refused to pay the medical expenses, they were wronged as the perpetrators by Liang's relatives. In addition to his wife, even his own son stood on the opposite side for a time. Few people around Qiao Anshan believe that there are selfless and fearless people like Lei Feng Qiao Anshan in today's society.
Qiao Anshan's true feelings on the radio awakened the conscience of the witness, and finally stood up to testify for Comrade Qiao Anshan. At the same time, the police arrested the driver who caused the accident, which really cleared the living Lei Feng. Otherwise, Qiao Anshan, a "mule puller", would probably be a "donkey thief".
Baidu Encyclopedia-Days of Leaving Lei Feng