After my wife gave birth to a male child, she underwent an operation to insert an intrauterine device (IUD) to prevent pregnancy.
(Part No. 19; Page No. 312) This is because the boy refused bottle-feeding and depended solely on breast milk for nourishment. In other words, we resorted to this birth control method to allow for a longer period for the child's full growth fearing that he might be negatively affected by abstention from bottle-feeding. The IUD was put with our mutual consent and we intended to remove it after the breastfeeding period was over. Later on, my wife died of heart failure when I was at work. I buried her (may Allah be merciful to her), having forgotten to remove the IUD as I was deeply shocked by the incident and only remembered one month later. Fearing Allah, I hope you give me a Fatwa in this regard. Are any of us, speaking about myself in particular, sinful? I am willing to do anything to ensure that Allah is pleased with her, because she was a righteous, religious wife. May Allah grant you success.
If the reality is as you mentioned, she is not sinful for using the IUD temporarily because she was concerned about the child's nourishment if she conceived. Consequently, neither you nor she is sinful for leaving the device in the uterus after your wife's death. Please find attached a copy of the decree issued by the Council of Senior Scholars regarding birth control for more information.