Messenger of Allah ﷺ forbade Ash-Shighar, which means that somebody marries his daughter to somebody else, and the latter marries his daughter to the former without paying Mahr.  

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الشِّغَارِ وَالشِّغَارُ أَنْ يُزَوِّجَ الرَّجُلُ ابْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ الآخَرُ ابْنَتَهُ لَيْسَ بَيْنَهُمَا صَدَاقٌ  

Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah ﷺ forbade shighar, which meant one man giving his daughter in marriage to another man on the condition that the other gave his daughter to him in marriage without either of them paying the bride-price.  

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الشِّغَارِ وَالشِّغَارُ أَنْ يُزَوِّجَ الرَّجُلُ ابْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ الآخَرُ ابْنَتَهُ لَيْسَ بَيْنَهُمَا صَدَاقٌ