The Ruling on One Who prayed while He was Junub
Question :
I was in a state of post-sex impurity and I prayed Fajr, Zuhr, Asr, Maghrib and Isha" (forgetting that I was Junub) and I did not remember until the following day. Should I repeat my prayers, or were they correct due to forgetfulness?
Answer:
You must repeat the prayers, because whoever prays while he is in a state of minor or major impurity, his prayer is invalid, even if it were due to forgetfulness, because he was negligent in his prayers. 'Umar bin Al-Khattab repeated his prayer when he remembered that he had had a nocturnal emission and had not made Ghusl.
Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 2 Pages 223