It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) forbade shighar. Shighar is when a man marries his daughter to another man on the condition that the other marries his daughter to him, with no dowry except this.

The marriage of Khansa bint Khidam was arranged by her father while she was previously married, and she was displeased with this marriage. She came to the Messenger of Allah, peace and blessings be upon him, and he annulled her marriage.

It is narrated from Abu Zubair that a mention was made before Sayyiduna Umar bin Khattab (may Allah be pleased with him) of a marriage in which there was no witness except for one man and one woman. He (may Allah be pleased with him) said: I do not consider this secret marriage permissible; if I had declared this earlier, I would have stoned (them) now.

It is narrated from Sa'id bin al-Musayyib and Sulayman bin Yasar that Talihah Asadiyyah was married to Rashid Thaqafi. He divorced her, so Talihah married another man during her 'iddah. Sayyiduna 'Umar, may Allah be pleased with him, flogged both of them and annulled the marriage. Then he said that if a woman marries another man during her 'iddah, and if consummation has not taken place, the marriage should be annulled and she should complete the remaining 'iddah of her first husband. After that, she may marry whomever she wishes, but she can never marry the second husband for the rest of her life. Sa'id bin al-Musayyib said that the woman can take her dowry from the second husband.

Imam Malik, may Allah have mercy on him, said: If a free woman’s husband dies and she completes her waiting period of four months and ten days, then if there is suspicion of pregnancy, she should not marry until that suspicion is removed or she gives birth.