The Cow - 2:232
When the divorced women have finished their waiting period, do not prevent them from remarrying if they agree with their husbands in goodness. Those of you who believe in Allah and the Last Day take admonition from this. That is purer and healthier for you. Allah knows, even if you do not know.
What is the waiting period for a woman if her husband dies?
The Cow/2:234
The wives left behind by the men who die among you wait four months and ten (days). When they have fulfilled their term, there is no responsibility on you to do what is suitable for them. Allah is All-Knowing of what you do.