حَدَّثَنَا يَحْيَى عَنْ عُبَيْدِ اللَّهِ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ نَهَى عَنْ نِكَاحِ الشِّغَارِ قَالَ قُلْتُ لِنَافِعٍ مَا الشِّغَارُ قَالَ يُزَوِّجُ الرَّجُلُ ابْنَتَهُ وَيَتَزَوَّجُ ابْنَتَهُ وَيُزَوِّجُ الرَّجُلُ أُخْتَهُ وَيَتَزَوَّجُ أُخْتَهُ بِغَيْرِ صَدَاقٍ
It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Noble Prophet (peace and blessings be upon him) forbade shighar. The narrator says: I asked Nafi‘, “What is shighar?” He said: It is when a man marries his daughter to another man and himself marries that man's daughter, or similarly, when a man marries his sister to another man and himself marries that man's sister, while there is no dowry (mahr) in between.