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. Allāh 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 period1 reaches its end. And know that Allāh knows what is within yourselves, so beware of Him. And know that Allāh is Forgiving and Forbearing.
Translation: Saheeh International (English)
1 The ʿiddah (bereavement period) after the death of a husband.
There is no sin on you if you hint to your desire to propose to a woman who is still in her waiting period after a divorce or after the death of her husband. For example, a person may say, ‘When your waiting period is over, let me know’. There is also no sin on you if you keep this desire to yourselves. Allah knows that you will mention them because of your strong desire to marry, so He has allowed you to give a hint without being open. Beware of secretly making any promise to marry them whilst they are still in their waiting period. However, you may give a hint to them in the manner that is acceptable; but do not confirm the marriage contract in the period of waiting. Know that Allah is aware of what is in your hearts, so be mindful of Him and do not go against His instruction. Know that Allah Forgiving to the person who repents to Him; and that He is tolerant and does not often quickly punish.