It was narrated that Bara bin Azib said:
“My maternal uncle passed by me - (one of the narrators) Hushaim named him in his narration as Harith bin Amr - and the Prophet ﷺ had given him a banner to carry. I said to him: 'Where are you going?’ He said: 'The Messenger of Allah ﷺ has sent me to a man who married his father's wife after he died, and has commanded me to strike his neck (i.e. execute him).”

حَدَّثَنَا إِسْمَاعِيلُ بْنُ مُوسَى، حَدَّثَنَا هُشَيْمٌ، ح وَحَدَّثَنَا سَهْلُ بْنُ أَبِي سَهْلٍ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ، جَمِيعًا عَنْ أَشْعَثَ، عَنْ عَدِيِّ بْنِ ثَابِتٍ، عَنِ الْبَرَاءِ بْنِ عَازِبٍ، قَالَ مَرَّ بِي خَالِي - سَمَّاهُ هُشَيْمٌ فِي حَدِيثِهِ الْحَارِثَ بْنَ عَمْرٍو - وَقَدْ عَقَدَ لَهُ النَّبِيُّ ﷺ لِوَاءً فَقُلْتُ لَهُ أَيْنَ تُرِيدُ فَقَالَ بَعَثَنِي رَسُولُ اللَّهِ ﷺ إِلَى رَجُلٍ تَزَوَّجَ امْرَأَةَ أَبِيهِ مِنْ بَعْدِهِ فَأَمَرَنِي أَنْ أَضْرِبَ عُنُقَهُ .