Sayyiduna Sahl bin Abi Hathmah (may Allah be pleased with him) said: Habibah bint Sahl (may Allah be pleased with her) was married to Thabit bin Qays bin Shammas al-Ansari (may Allah be pleased with him), and she came to dislike him; Thabit was an unattractive man. So she came to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah, by Allah, when I see him, were it not for the fear of Allah, I would spit in his face." The Messenger of Allah (peace and blessings be upon him) said: "Will you return to him the garden that he gave you as your dowry (mahr)?" She said: "Yes." So he (peace and blessings be upon him) sent for Thabit, and Habibah returned the garden to him, and he (peace and blessings be upon him) separated the two of them. This was the first khul' in Islam.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20938