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كتاب النكاح
67  
Wedlock, Marriage (Nikaah)
(35)
Chapter: "And there is no sin on you if you make a hint of betrothal or conceal it in yourself..."
(34)
باب قَوْلِ اللَّهِ جَلَّ وَعَزَّ : {وَلاَ جُنَاحَ عَلَيْكُمْ فِيمَا عَرَّضْتُمْ بِهِ مِنْ خِطْبَةِ النِّسَاءِ أَوْ أَكْنَنْتُمْ فِي أَنْفُسِكُمْ عَلِمَ اللَّهُ} الآيَةَ إِلَى قَوْلِهِ: {غَفُورٌ حَلِيمٌ}
Sahih al-Bukhari 5124
Ibn `Abbas said:

"Hint your intention of marrying' is made by saying (to the widow) for example: "I want to marry, and I wish that Allah will make a righteous lady available for me.' " Al-Qasim said: One may say to the widow: 'I hold all respect for you, and I am interested in you; Allah will bring you much good, or something similar 'Ata said: One should hint his intention, and should not declare it openly. One may say: 'I have some need. Have good tidings. Praise be to Allah; you are fit to remarry.' She (the widow) may say in reply: I am listening to what you say,' but she should not make a promise. Her guardian should not make a promise (to somebody to get her married to him) without her knowledge. But if, while still in the Iddat period, she makes a promise to marry somebody, and he ultimately marries her, they are not to be separated by divorce (i.e., the marriage is valid).

وَقَالَ لِي طَلْقٌ حَدَّثَنَا زَائِدَةُ، عَنْ مَنْصُورٍ، عَنْ مُجَاهِدٍ، عَنِ ابْنِ عَبَّاسٍ، ‏{‏فِيمَا عَرَّضْتُمْ‏}‏ يَقُولُ إِنِّي أُرِيدُ التَّزْوِيجَ، وَلَوَدِدْتُ أَنَّهُ تَيَسَّرَ لِي امْرَأَةٌ صَالِحَةٌ‏.‏ وَقَالَ الْقَاسِمُ يَقُولُ إِنَّكِ عَلَىَّ كَرِيمَةٌ، وَإِنِّي فِيكِ لَرَاغِبٌ، وَإِنَّ اللَّهَ لَسَائِقٌ إِلَيْكِ خَيْرًا‏.‏ أَوْ نَحْوَ هَذَا‏.‏ وَقَالَ عَطَاءٌ يُعَرِّضُ وَلاَ يَبُوحُ يَقُولُ إِنَّ لِي حَاجَةً وَأَبْشِرِي، وَأَنْتِ بِحَمْدِ اللَّهِ نَافِقَةٌ‏.‏ وَتَقُولُ هِيَ قَدْ أَسْمَعُ مَا تَقُولُ‏.‏ وَلاَ تَعِدُ شَيْئًا وَلاَ يُوَاعِدُ وَلِيُّهَا بِغَيْرِ عِلْمِهَا، وَإِنْ وَاعَدَتْ رَجُلاً فِي عِدَّتِهَا ثُمَّ نَكَحَهَا بَعْدُ لَمْ يُفَرَّقْ بَيْنَهُمَا‏.‏ وَقَالَ الْحَسَنُ ‏{‏لاَ تُوَاعِدُوهُنَّ سِرًّا‏}‏ الزِّنَا‏.‏ وَيُذْكَرُ عَنِ ابْنِ عَبَّاسٍ ‏{‏الْكِتَابُ أَجَلَهُ‏}‏ تَنْقَضِي الْعِدَّةُ‏.‏
Reference : Sahih al-Bukhari 5124
In-book reference : Book 67, Hadith 60
USC-MSA web (English) reference : Vol. 7, Book 62, Hadith 56
  (deprecated numbering scheme)