Hisham bin Urwah (may Allah have mercy on him) narrates from his father that this verse was revealed concerning Sayyidah Sawdah (may Allah be pleased with her) and women like her: "And if a woman fears from her husband ill-conduct or desertion" [Surah al-Nisa: 128]. That is, Sayyidah Sawdah (may Allah be pleased with her) was a woman who had grown old, and she became anxious that the Messenger of Allah (peace and blessings be upon him) might separate from her. She knew of the love of the Messenger of Allah (peace and blessings be upon him) for Sayyidah Aishah (may Allah be pleased with her) and of her rank and position, so she gifted her turn to Sayyidah Aishah (may Allah be pleased with her), and the Messenger of Allah (peace and blessings be upon him) accepted it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسم والنشوز / 14736