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  

It was narrated from Ibn 'Umar that the Messenger of Allah forbade Ash-Shighar. Ash-Shighar means when a man marries his daughter to another man, on the condition that that man marries his daughter to him, and no dowry is exchanged between them.  

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الشِّغَارِ وَالشِّغَارُ أَنْ يُزَوِّجَ الرَّجُلُ الرَّجُلَ ابْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ ابْنَتَهُ وَلَيْسَ 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  

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. (Using translation from Bukhārī 5112)  

أَنَّ رَسُولَ اللهِ ﷺ «نَهَى عَنِ الشِّغَارِ وَالشِّغَارُ أَنْ يُزَوِّجَ الرَّجُلُ الرَّجُلَ ابْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ ابْنَتَهُ وَلَيْسَ بَيْنَهُمَا صَدَاقٌ»