Shafaqna (Shia International News Association) – The Grand Ayatollah Sistani answered some questions regarding Doubts.According to Shafaqna the questions and answers are as follows:
Question1 : Can Muslim, who rents a fully furnished house in the West, consider everything in it to be ritually pure as long as he does not find any trace of impure things in it, even if the previous occupant was from Ahlul Kitab, i.e., a Christian or a Jew? What if the previous occupant was a Bhuddhist or an atheist who does not believe in God and the prophets?
Answer: Yes, he can consider everything in the house ritually pure as long as he does not know that it has become impure. Just conjecture or doubt about impurity is of no value.
Question2: If a person has a lot of doubts in Wudu’, prayer, Ghusl etc. what should he do?
Answer: He should not pay heed to his doubt and keep on considering it as valid (Sahih).
Question3: Even though some manufacturers write on their products that they have been made of natural silk, we doubt such a claim because of the goods very low price. Is it permissible for us to wear such an item and say salãt in it?
Answer: With doubt [whether the silk is pure], it is permissible to wear and say salãt in it.
Source: Ayatollah Sistani