Al-Baqarah 2:234

وَٱلَّذِينَ يُتَوَفَّوۡنَ مِنكُمۡ وَيَذَرُونَ أَزۡوَٰجٗا يَتَرَبَّصۡنَ بِأَنفُسِهِنَّ أَرۡبَعَةَ أَشۡهُرٖ وَعَشۡرٗاۖ فَإِذَا بَلَغۡنَ أَجَلَهُنَّ فَلَا جُنَاحَ عَلَيۡكُمۡ فِيمَا فَعَلۡنَ فِيٓ أَنفُسِهِنَّ بِٱلۡمَعۡرُوفِۗ وَٱللَّهُ بِمَا تَعۡمَلُونَ خَبِيرٞ 234

And those who are taken in death among you and leave wives behind - they, [the wives, shall] wait four months and ten [days]. And when they have fulfilled their term, then there is no blame upon you for what they do with themselves in an acceptable manner. And Allah is [fully] Acquainted with what you do