Question : a) Is there any proof of Istikhara in the Sharia?
b) Is everybody allowed to do Isikhara for himself?
c) What are the rules of Istikhara and is it allowed to repeat an Isikhara for the same occasion?
Answer : There were narrations that explained the idea of Istikhara which is seeking goodness from almighty Allah when deciding to do a thing. This kind of Istikhara is the most common in the narrations. Books of narrations and supplications have explained certain ways to do the Istikhara.
Yes, it is apparent in some texts that Istikhara is seeking help in deciding the better position in cases of hesitance and uncertainty in finding out the best choice for a person. These narrations did not specify the person that must do the Istikhara, so anyone is allowed to do it themselves or to ask others.
There are no specific conditions for the Istikhara but it is supposed to be done when the right choice is unknown.
Then it is meaningless to repeat it after it has been done.
Question : On the internet, there are websites which allow you to do istikharah by the Quran. A supplication is first recited and then a random verse will be presented on clicking a button. Is it valid to do Istikhara in this manner?
Answer : It has been reported in some narrations to perform the Istikhara with the actual Quran just before offering the prayer. What you mention does not relate to this.
Question : Is there a specific time for doing Istikhara using the Holy Quran?
Answer : Some narrations determine the time of Istikhara using the Holy Quran to be during the time of the prayers.
Question : If a man proposes to a woman and his faith and manners are good, is it then recommended or permissible to resort to Istikhara for the sake of knowing whether the marriage will be good or not or should the proposal be accepted on the basis of his virtue?
Answer : As long as the proposed man is religious and virtuous, it is better to accept him for marriage since the encouragement to accept such person is reported in many narrations, although it is permissible to refer to Istikhara.
Question : In the circumstance of two people who are happy with each other’s religion and behaviors and there is no doubt in their minds of wanting to marry one another, would an Istikhara be required to try and find out if they should get married?
Answer : Istikhara is not obligatory but it was narrated that it is used when there is doubt in the person’s mind. Istikhara for marriage when the conditions are met does not correspond to what is reported in the narrations about accepting a person for marriage when the conditions are met. Yes. It is better to seek the goodness from the Almighty and depend on Him.
Question : I had done Istikhara for a particular matter and I acted according to it then. However, after some time had passed the same issue arose again. If I act differently, will I be going against the Istikhara?
Answer : The original Istikhara was done according to the current circumstances then. The passage of time leads to different circumstances, so acting differently this time will not be considered going against the original Istikhara.
Depending on Istikhara
Question :

Is it permissible to rely on istikhara to determine the most knowledgeable jurist amongst the qualified mujtahids?

Answer :

It is not permissible to depend on istikhara in determining one's marja.

Question : Can an Istikhara be used to find the outcome of an event like marriage, contracts and business?
Answer : Istikhara is not for telling the future.
Istikhara in Marraige
Question :

Is it permissible to rely on the result of the Istikhara and accept the man for marriage without the approval of the girl?

Answer :

It is obligatory to seek the best interests of the girl, and her acceptance is necessary in marriage.