Al-Baqarah 2:235

Wala junaha AAalaykum feemaAAarradtum bihi min khitbati annisa-iaw aknantum fee anfusikum AAalima Allahu annakum satathkuroonahunnawalakin la tuwaAAidoohunna sirran illaan taqooloo qawlan maAAroofan wala taAAzimoo AAuqdata annikahihatta yablugha alkitabu ajalahu waAAlamooanna Allaha yaAAlamu ma fee anfusikum fahtharoohuwaAAlamoo anna Allaha ghafoorun haleem

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 period reaches its end. And know that Allāh knows what is within yourselves, so beware of Him. And know that Allāh is Forgiving and Forbearing.

There is no sin on you if you hint as a proposal to the women, or conceal it in your hearts. Allah knows that you will make mention of them. But do not make a promise to them secretly, except that you speak in a recognized manner. Nor resolve upon a contract of marriage until the prescribed time is reached. Be assured that Allah knows what is in your hearts. So, fear Him and be assured that Allah is most Forgiving, Forbearing.