In the age before Islam there was a custom: if a husband in anger told his wife 'you are to me like my mother's back' — called zihar — she was neither divorced nor treated as a wife; she was left hanging.
When Khawlah bint Tha'labah's husband said this, she came to the Messenger of Allah ﷺ, told him of her helplessness, and kept pleading her case to Allah. Then Allah revealed the opening verses of Surah al-Mujadilah:
قَدۡ سَمِعَ ٱللَّهُ قَوۡلَ ٱلَّتِي تُجَٰدِلُكَ فِي زَوۡجِهَا وَتَشۡتَكِيٓ إِلَى ٱللَّهِ وَٱللَّهُ يَسۡمَعُ تَحَاوُرَكُمَآۚ إِنَّ ٱللَّهَ سَمِيعُۢ بَصِيرٌ
“Certainly has Allāh heard the speech of the one who argues [i.e., pleads] with you, [O Muḥammad], concerning her husband and directs her complaint to Allāh. And Allāh hears your dialogue; indeed, Allāh is Hearing and Seeing.”
Surah Al-Mujadila 58:1
Translation: Saheeh International (QuranEnc)
The verses abolished this unjust custom and set an expiation for it. From one ordinary woman's plea came a ruling that protected women from this injustice for ever.
ⓘ The Quran does not name the woman here; the name Khawlah bint Tha'labah comes from the hadith and tafsir works.