Does a mother's remarriage void her right to custody?
Chapter on Who is More Entitled to Child Custody
Al-Mughni
Book of Maintenance (Nafaqāt)
Primary text
Upon the mother's remarriage, her right to custody is forfeited. This is the consensus among scholars whose opinions are recorded, including the ruling by Shurayh, and is the position of Malik, Al-Shafi'i, and the Hanafis (As'hab al-Ra'y). The primary evidence supporting this forfeiture is the Prophet's statement to a woman: 'You are more entitled to him, until you marry.' When the mother marries, the rights of the husband take precedence over the duties of custody, making the father more entitled. Furthermore, the mother's benefits become owned by another, resembling servitude.
Supporting text
A narration concerning the custody of Hamza's daughter, where the Prophet judged in favor of Ja'far's wife (the paternal aunt) over Ali, is explained by the fact that Ja'far's wife was married to a relative eligible for custody (the aunt being the mother's equivalent). Thus, when the woman is married to a relative eligible for custody, such as a grandmother married to the grandfather, her custody right is not forfeited because the husband shares in the affection for the child, analogous to the mother being married to the father. A potential difference in ruling exists regarding a young boy versus a girl: some narration suggests the right is only removed from the boy upon the mother's remarriage, while the girl remains with her mother until seven years of age.