Hadith 483
Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) reports: The Messenger of Allah (peace and blessings be upon him) said: "Shighar is not permissible." Someone asked: What is shighar? He (peace and blessings be upon him) said: "It is to marry a woman in exchange for marrying another woman, with no dowry stipulated between them."