And those of you who die and leave wives behind them, they (the wives) shall wait (as regards their marriage) for four months and ten days, then when they have fulfilled their term, there is no sin on you if they (the wives) dispose of themselves in a just and honourable manner (i.e. they can marry). And Allâh is Well-Acquainted with what you do. (2:234)

And there is no sin on you if you make a hint of betrothal or conceal it in yourself, Allâh knows that you will remember them, but do not make a promise of contract with them in secret except that you speak an honorable saying according to the Islâmic law (e.g. you can say to her, "If one finds a wife like you, he will be happy"). And do not consummate the marriage until the term prescribed is fulfilled. And know that Allâh knows what is in your minds, so fear Him. And know that Allâh is Oft-Forgiving, Most Forbearing. (2:235)