﴿ لِّئَلَّا يَعْلَمَ أَهْلُ ٱلْكِتَٰبِ أَلَّا يَقْدِرُونَ عَلَىٰ شَىْءٍۢ مِّن فَضْلِ ٱللَّهِ ۙ وَأَنَّ ٱلْفَضْلَ بِيَدِ ٱللَّهِ يُؤْتِيهِ مَن يَشَآءُ ۚ وَٱللَّهُ ذُو ٱلْفَضْلِ ٱلْعَظِيمِ ﴾

“And the followers of earlier revelation should know that they have no power whatever over any of God’s bounty, seeing that all bounty is in God’s hand [alone]: He grants it unto whomever He wills - for God is limitless in His great bounty.”

Before Islam, it was the custom in Arabia that if a man said to his wife, ‘To me you are like my mother’s back’ she was for ever forbidden for that man. This was called zihar. A Muslim of Madinah, Aws ibn as-Samit, once repeated these very words to his wife, Khawlah bint Tha‘labah. She came to the Prophet and related the incident. The Prophet, taking into account the old custom, opined that she stood forbidden for Aws ibn as-Samit. Khawlah was worried that her house and her children would be destroyed, and she started crying and wailing. On this occasion these verses were revealed and the Islamic rules on zihar were laid down.