
If a woman does not sit in iddah after the death of her husband, will she be an offender?

Bismillahi Ta’ala
Walaikum Assalam Warahmatullah,
Iddah is a wajib imposition established from Qur’an, and thus it is in the rank of fardh ruling. Violation or breaking it is same is being disobedient with a fardh ruling of Allah.
Allah Ta’ala says, “Those among you who pass away and leave wives behind, their wives keep themselves waiting for four months and ten days. So, when they have reached (the end of) their waiting period, there is no sin on you in what they do for themselves in recognized manner. Allah is All-Aware of what you do.” (Qur’an 2:234)
Wallahu A’lam
And Allah Ta’āla Knows Best
Mufti Faisal al-Mahmudi