Nafi' said that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) "forbade shighar". I asked Nafi': What is shighar? He said: A man marries another man's daughter and his own daughter is married to that man, with no dowry between them; and he marries another man's sister and his own sister is married to the other, without dowry.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14135