Hadith 22

Bulugh al-Maram

Book 8: Marriage
وَعَنْ نَافِعٍ , عَنْ اِبْنِ عُمَرَ قَالَ : { نَهَى رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-عَنِ الشِّغَارِ ; وَالشِّغَارُ: أَنْ يُزَوِّجَ اَلرَّجُلُ اِبْنَتَهُ عَلَى أَنْ يُزَوِّجَهُ اَلْآخَرُ اِبْنَتَهُ , وَلَيْسَ بَيْنَهُمَا صَدَاقٌ } مُتَّفَقٌ عَلَيْهِ 1‏ .‏
Nafi' from Ibn 'Umar (RA):

Allah's Messenger (ﷺ) prohibited Shighar, which means that a man gives his daughter in marriage on condition that the other gives his daughter to him in marriage [in exchange] without any dowry being paid by either. [Agreed upon].