Yahya related to me from Malik that he had heard that Said ibnal-Musayyab was asked about a woman who made a stipulation on herhusband not to take her away from her town. Said ibn al-Musayyab said,"He takes her away if he wishes."Malik said, "The customamong us is that when a man marries a woman, and he makes a conditionin the marriage contract that he will not marry after her or take aconcubine, it means nothing unless there is an oath of divorce orsetting-free attached to it. Then it is obliged and required of him."
USC-MSA web (English) reference: Book 28, Hadith 16
Arabic reference: Book 28, Hadith 1110