Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:2:235 –

There is no blame upon you for that to which you ˹indirectly˺ allude concerning a proposal to women or for what you conceal within yourselves. Allah knows that you will have them in mind. But do not promise them secretly except for saying a proper saying. And do not determine to undertake a marriage contract until the decreed period reaches its end. And know that Allah knows what is within yourselves, so beware of Him. And know that Allah is Forgiving and Forbearing.  

You would not be at fault regarding the proposal, with the intention of marriage, you present, offer, or hide in your hearts, during the waiting period, to women, whose spouses have died: such as men saying, ‘How beautiful you are!’, or, ‘Who could find one like you?’, or ‘How many a man must desire you!’. God knows that you will be mindful of them, in proposing to them impatiently, and so He has permitted you to make such offers; but do not make arrangements, of marriage, with them secretly, unless you speak honourable words, such as are acknowledged by the Law, in other words, such as proposals, that which is permitted to you. And do not resolve on the knot, the consummation, of marriage until that which is written, the period prescribed, has reached its term, and has been completed; and know that God knows what is in your souls, of resolve or otherwise; so be fearful of Him, that He should chastise you if you have made such resolve; and know that God is Forgiving, toward him who is fearful of Him, Forbearing, in delaying the chastisement of the one deserving it.
القرآن:٢:٢٣٥ –

وَلَا جُنَاحَ عَلَيْكُمْ فِيمَا عَرَّضْتُمْ بِهِ مِنْ خِطْبَةِ النِّسَاءِ أَوْ أَكْنَنْتُمْ فِي أَنْفُسِكُمْ ۚ عَلِمَ اللَّهُ أَنَّكُمْ سَتَذْكُرُونَهُنَّ وَلَٰكِنْ لَا تُوَاعِدُوهُنَّ سِرًّا إِلَّا أَنْ تَقُولُوا قَوْلًا مَعْرُوفًا ۚ وَلَا تَعْزِمُوا عُقْدَةَ النِّكَاحِ حَتَّىٰ يَبْلُغَ الْكِتَابُ أَجَلَهُ ۚ وَاعْلَمُوا أَنَّ اللَّهَ يَعْلَمُ مَا فِي أَنْفُسِكُمْ فَاحْذَرُوهُ ۚ وَاعْلَمُوا أَنَّ اللَّهَ غَفُورٌ حَلِيمٌ  

{ولا جُناح عليكم فيما عَرَّضتم} لوحتم {به من خطبة النساء} المتوفى عنهن أزواجهن في العدة كقول الإنسان: مثلا إنك لجميلة ومن يجد مثلك ورب راغب فيك {أو أكننتم} أضمرتم {في أنفسكم} من قصد نكاحهن {علم الله أنكم ستذكرونهن} بالخطبة ولا تصبرون عنهن فأباح لكم التعريض {ولكن لا تواعدوهن سرّاً} أي نكاحاً {إلا} لكن {أن تقولوا قولاً معروفا} أي ما عرف لكم شرعا من التعريض فلكم ذلك {ولا تعزموا عقدة النكاح} أي على عقده {حتى يبلغ الكتاب} أي المكتوب من العدة {أجله} بأن ينتهي {واعلموا أن الله يعلم ما في أنفسكم} من العزم وغيره {فاحذروه} أن يعاقبكم إذا عزمتم {واعلموا أن الله غفور} لمن يحذره {حليم} بتأخير العقوبة عن مستحقها.

See similar narrations below:

Collected by Mālik
malik:28-3 – Mālik > ʿAbd al-Raḥman b. al-Qāsim from his father

Yahya related to me from Malik from Abd ar-Rahman ibn al-Qasim that his father said about the word of Allah, the Blessed, the Exalted, "There is no fault in you about the proposal you offer to women, or hide in yourselves. Allah knows that you will be mindful of them; but do not make troth with them secretly without honourable words," (Sura 2 ayat 235) that it referred to a man saying to a woman while she was still in her idda after the death of her husband, "You are dear to me, and I desire you, and Allah brings provision and blessing to you," and words such as these.  

مالك:٢٨-٣ – وَحَدَّثَنِي عَنْ مَالِكٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ الْقَاسِمِ عَنْ أَبِيهِ

أَنَّهُ كَانَ يَقُولُ فِي قَوْلِ اللَّهِ تَبَارَكَ وَتَعَالَى وَلاَ جُنَاحَ عَلَيْكُمْ فِيمَا عَرَّضْتُمْ بِهِ مِنْ خِطْبَةِ النِّسَاءِ أَوْ أَكْنَنْتُمْ فِي أَنْفُسِكُمْ عَلِمَ اللَّهُ أَنَّكُمْ سَتَذْكُرُونَهُنَّ وَلَكِنْ لاَ تُوَاعِدُوهُنَّ سِرًّا إِلاَّ أَنْ تَقُولُوا قَوْلاً مَعْرُوفًا أَنْ يَقُولَ الرَّجُلُ لِلْمَرْأَةِ وَهِيَ فِي عِدَّتِهَا مِنْ وَفَاةِ زَوْجِهَا إِنَّكِ عَلَىَّ لَكَرِيمَةٌ وَإِنِّي فِيكِ لَرَاغِبٌ وَإِنَّ اللَّهَ لَسَائِقٌ إِلَيْكِ خَيْرًا وَرِزْقًا وَنَحْوَ هَذَا مِنَ الْقَوْلِ