《左传·定公·定公四年》
苌弘很高兴，告诉了刘子，和范献子商量这件事，在结盟时就让卫侯在蔡侯之前歃血。
苌弘说，告刘子，与范献子谋之，乃长卫侯于盟。
Zhang Hong was very happy.  He told Liu Zi.  He consulted Fan Xianzi.  They had the Duke of Wei swear before the Duke of Cai when they made the covenant.