What is the ruling concerning a wife who does not observe her waiting period (iddah) after the death of her husband?

The 'iddah (waiting period) for a woman whose husband has died is four months and ten days, unless she is pregnant, in which case her 'iddah ends upon delivery. She must remain in her home and refrain from adornment. If she violates these rules without a valid excuse, she commits a sin and must repent. Her 'iddah concludes upon the delivery of her child or the expiry of the aforementioned period, and she is not required to make up any missed days.