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 blame upon you whether you hint at a marriage proposal to such women or keep the proposal hidden in your hearts. Allah knows that you will think of them in that connection. But do not make any secret engagement with them and speak openly in an honourable manner. Do not resolve on the marriage tie until the ordained term has come to its end. Know well that Allah knows even what is in your hearts. So, have fear of Him and know well that Allah is All-Forgiving, All-Forbearing.