Ishaq bin Yusuf bin Mrdas إسحاق بن يوسف بن مرداس · The Book of Marriage

"I met my maternal uncle who was carrying a flag (for an expedition) and I said: 'Where are you going?' He said: 'The Messenger of Allah is sending me to a man who has married his father's wife, and he has commanded me to strike his neck (kill him) and seize his wealth.'"