Bulugh al-Maram 8 Marriage كتاب النكاح 22

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 . 1 – صحيح . رواه البخاري ( 5112 ) ، ومسلم (1415).

Narrated Nafi’ from Ibn ‘Umar (RA): Allah’s Messenger (صلى الله عليه وسلم) 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].