《史记·三十世家·留侯世家》
这四个人互相商议说： 我们之所以来，是为了要保全太子，太子如若率兵平叛，事情就危险了。 
四人相谓曰： 凡来者，将以存太子。太子将兵，事危矣。 
The four discussed among themselves that “Our purpose in coming was to protect the crown prince, if the crown prince leads troops to quell the rebellion, then things will be dangerous.”