《资治通鉴·汉纪·汉纪六十》
孙权写信给魏王曹操，请求允许他讨伐关羽，为朝廷效力，并请求不要把消息泄漏出去，使关羽有所防范。
孙权为笺与魏王操，请以讨羽自效，及乞不漏，令羽有备。
Sun Quan wrote to King Cao of Wei, asking for permission to attack Guan Yu so as to serve the court and requesting that the message be kept confidential so that Guan Yu would not be alerted.