Al-Baqarah 2:235 ولا جناح عليكم فيما عرضتم به من خطبة النساء او اكننتم في انفسكم علم الله انكم ستذكرونهن ولاكن لا تواعدوهن سرا الا ان تقولوا قولا معروفا ولا تعزموا عقدة النكاح حتى يبلغ الكتاب اجله واعلموا ان الله يعلم ما في انفسكم فاحذروه واعلموا ان الله غفور حليم ٢٣٥

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.