وَعَنْ نَافِعٍ، عَنْ اِبْنِ عُمَرَ
قَالَ: «نَهَى رَسُولُ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنِ الشِّغَارِ ; وَالشِّغَارُ: أَنْ يُزَوِّجَ اَلرَّجُلُ اِبْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ اَلْآخَرُ اِبْنَتَهُ، وَلَيْسَ بَيْنَهُمَا صَدَاقٌ»
The Messenger of Allah (sallallahu alayhi wa sallam) prohibited Shighar, which means that a man gives his daughter in marriage on condition that the other gives his daughter to him in marriage without any dowry being paid by either.
Bulugh al-Maram 1144, Book 8, Marriage, Hadith 22. 1 min read