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  

"The Messenger of Allah forbade Ash-Shighar." (One of the narrators) 'Ubaidullah said: "Ash-Shighar means when a man gives his daughter in marriage on condition that (the other man) gives him his sister in marriage."  

نَهَى رَسُولُ اللَّهِ ﷺ عَنِ الشِّغَارِ قَالَ عُبَيْدُ اللَّهِ وَالشِّغَارُ كَانَ الرَّجُلُ يُزَوِّجُ ابْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ أُخْتَهُ