Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: Sawdah (may Allah be pleased with her) feared that the Prophet (peace and blessings be upon him) would divorce her, so she said: O Messenger of Allah! Keep me and do not divorce me, and give my turn to Aishah. So Allah, the Mighty and Majestic, revealed: "There is no sin on them both" if they make a settlement between themselves, and settlement is better; and whatever they settle upon is permissible.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20456