حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى بْنِ فَارِسٍ، حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا أَبِي، عَنِ ابْنِ إِسْحَاقَ، حَدَّثَنِي عَبْدُ الرَّحْمَنِ بْنُ هُرْمُزَ الأَعْرَجُ، أَنَّ الْعَبَّاسَ بْنَ عَبْدِ اللَّهِ بْنِ الْعَبَّاسِ، أَنْكَحَ عَبْدَ الرَّحْمَنِ بْنَ الْحَكَمِ ابْنَتَهُ وَأَنْكَحَهُ عَبْدُ الرَّحْمَنِ ابْنَتَهُ وَكَانَا جَعَلاَ صَدَاقًا فَكَتَبَ مُعَاوِيَةُ إِلَى مَرْوَانَ يَأْمُرُهُ بِالتَّفْرِيقِ بَيْنَهُمَا وَقَالَ فِي كِتَابِهِ هَذَاالشِّغَارُ الَّذِي نَهَى عَنْهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏

Abdur Rahman ibn Hurmuz al-A'raj said

Al-Abbas ibn Abdullah ibn al-Abbas married his daughter to Abd al-Rahman ibn al-Hakam, and Abd al-Rahman married his daughter to him, and they had made that their dowry. Mu'awiyah wrote to Marwan commanding him to separate them, and he said in his letter: This is the shighar which the Messenger of Allah (ﷺ) forbade.