When is it allowed to do "Mubahalah"? [1]

Are there any needed conditions so that we can do Mubahalah? Or anyone can do it for proving his/her faith? Which case is it allowed to do it in? Has it surely happened throughout the history of Islam? According to the Holy Qur’an, what happened was to suggest it from the Holy Prophet (P.B.U.H.), and Mubahalah didn’t happen (because the Najrani Christians rejected the suggestion). Is it right?

Mubahalah means to curse each other so that anyone who is false will be subject to the divine anger and the one who is right will be known and, in this way, right will be distinguished from wrong.

I

t is a kind of prayer (Dua) having some properties and conditions that we point to of them in the following:

1- to reform himself/herself morally for 3 days        2- to take Sawm (fasting) 

3- to do Ghusl (bathing)              4- to go to a desert with someone whom s/he wants to do it with  

5- do it between dawn and sunrise.

Mubahala is not specific to the time of the Holy Prophet Mohammad (P.B.U.H.), but other believers can do it. Thus, everyone is allowed to do it for proving his/her legitimacy against the enemies of Islam by observing the above-mentioned conditions. Of course, we should note that the conditions of Mubahalah and sincerity and the self-confidence that are needed for it are not easily achievable for everyone. So, we shouldn’t do it hurriedly. Since it might have the opposite effect after that.

Meanwhile, it should be known that Mubahalah is specific to those religious disputes and conflicts that the opposite party (despite the logical and scientific arguments and discussions) does not accept the right and the truth and insists on his/her false opinion.

Based on the interpretations of the related verses, it is known that the Mubahalah of the Holy Prophet Mohammad (P.B.U.H.) finally ended with peace and tranquility.

[1]. Reference: islamquest.net