Al-Baqara 2:234

Those among you who pass away and leave behind widows should refrain from remarrying for four months and ten days. When they have completed their waiting period, there is no sin on you concerning what they do for themselves[127] in a reasonable manner[128]. And Allah is All-Aware of what you do.

[127] They may remarry if they wish.
[128] A social norm that entails keeping within the dictates of Islam.

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.[92] And Allāh is [fully] Aware of what you do.

[92] They may remarry if they wish.

234. 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.

Such of you as die and leave behind them wives, they (the wives) shall wait, keeping themselves apart, four months and ten days. And when they reach the term (prescribed for them) then there is no sin for you in aught that they may do with themselves in decency. Allah is informed of what ye do.