《史记·三十世家·燕召公世家》
苏秦和燕文公的夫人通奸，害怕被杀掉，于是就游说易王派他出使齐国去搞反间，借以扰乱齐国。
苏秦与燕文公夫人私通，惧诛，乃说王使齐为反间，欲以乱齐。
Su Qin committed adultery with the wife of Duke Wen of Yan, and was afraid of being killed, so he lobbied King Yi to send him to Qi to engage in counterespionage, in order to disturb Qi.