One who prays and then remembers two hours later that he was not in a state of ritual purity

Question:
I was traveling, and the time for the Maghrib prayer entered. We prayed Maghrib and 'Isha', and two hours later I remembered that I was not in a state of wudu'. What is the ruling in this case?

Answer:
The ruling is that you must perform wudu' and repeat both prayers, because they were not valid for you due to the lack of ritual purity. Ritual purity is a condition for the validity of the prayer, and wudu' is what is excused from you by forgetfulness.