Q. 504. After completing his ‘Umrah, a man found some filth in his Ihram garments; what is the ruling on this?
A. If a person performed Tawaf and Say for ‘Umrah, and after that, he found some filth in his Ihram garments, then his Tawaf is valid, his Say is valid and his ‘Umrah is valid. This is because if a person has some filth on his garment, and he does not know about it, or he knew about it but he forgot to wash it, and then he prayed in that garment, then his prayer is valid. Similarly, if he made Tawaf in this garment, then his Tawaf is valid. The evidence for that is the Saying of Allah, the Most High:
“Our Lord! Punish us not if we forget or fall into error” [Al-Baqarah 2:286]
This evidence is general, and it is considered a great rule from among the rules of Islamic Law. There is a specific evidence in the matter, and that is that one day, the Messenger of Allah (صلى الله عليه و سلم) led his Companions, may Allah be pleased with them, in prayer and it was his practice to pray in his shoes, but he removed his shoes and the people removed their shoes too. After he had finished praying, he said to them: What was wrong with you?
They said: “We saw you removing your shoes.”
He said: “Jibril came to me and informed me that there was something harmful or some dirt on them” 
That is, some impurity. The Prophet (صلى الله عليه و سلم) did not repeat the prayer, even though at the beginning of his prayer, he had worn shoes on which there was some impurity. This proves that if a person prayed in a garment in which there was impurity due to forgetfulness or ignorance, his prayer is valid.
There is a question here: If a person eats camel meat and he stands up and prays without performing ablution, believing that he had eaten mutton, should he repeat his prayer if he found out? We say: He should repeat the prayer after performing ablution. If someone asked: Why do you say that a person who prayed in a polluted garment due to ignorance should not repeat the prayer, while one who eats camel meat due to ignorance, should repeat it? We say: Because we have a useful and important rule, which is, commands are not cancelled due to ignorance or forgetfulness, whereas prohibitions are cancelled due to ignorance and forgetfulness. The evidence for this rule is the saying of the Prophet (صلى الله عليه و سلم):
“Whoever slept through a prayer or forgot it, he must offer it as soon as he remembers it.” 
And when he made the Taslim after performing two Rak’at in one of his afternoon prayers and he forgot the remainder of the prayer, he completed it when he remembered it. This is an evidence that those things which are commanded are not cancelled due to forgetfulness, because the Prophet ordered the one who forgot his prayer to offer it as soon as he remembers it, and the obligation to pray it was not removed due to forgetfulness. Also, he completed the prayer and he did not cancel the remainder of it due to forgetfulness. The proof that commands are not cancelled due to ignorance, is that a man came and offered a prayer in which he was not at rest, then he came to the Prophet (صلى الله عليه و سلم) and greeted him and he said to him:
“Go back and offer prayer for you have not prayed.”
He repeated it three times and the man kept praying and coming to him, but he would say:
“Go back and offer prayer, for you have not prayed.”
until the Prophet (صلى الله عليه و سلم) taught him to pray correctly. So,this man abandoned an obligatory act due to ignorance, because he said:
“By Him Who sent you with the truth, I cannot pray better than this, so teach me.” If an obligation was cancelled due to ignorance, the Prophet (صلى الله عليه و سلم) would have excused him; and this rule is important and beneficial for the seeker of knowledge.
 Reported by Abu Dawud in the Book of Prayer (650)
 Reported by Al-Bukhari in the Book of the Times of the Prayers, in the Chapter: Whoever Forgot a Prayer, The He Must Pray it When he Remembers Hadith (597); and by Muslim in the Book of Masjids, in the Chapter: Making up for the Prayers Hadith 316.
Fatawa Arkanul-Islam -Islamic Verdicts on the Pillars of Islam (Volume Two)
Prayer, Zakah, Fasting, Hajj
By the Honorable Shaikh Muhammad bin Salih Al- ‘Uthaimeen
Collected and Arranged by Fahd bin Nasir bin Ibrahim As-Sulaiman