The event of Mubahilah took place in the 9th year of Hijra. A deputation of 14 Christian (najran) scholars came to discuss the truth of Islam with the Holy Prophet (sa) Arguments were put forward by both sides. Several days went by The Christians did not listen to reason.
Then Allah revealed the following verses:
"Verily, the likeness of Eessa with Allah is as the likeness of Aadam. He created him of dust, then He said unto him:Be, and he was (This is ) the truth from your Lord (O Muhammad), so be not of those who doubt.
And whoso disputes with you concerning him after the knowledge which has come unto you, say (unto them): Come We will summon our sons and you your sons, and our women and you your women, and our selfs and your selfs, and then will pray humbly (to the Lord) and invoke the curse of Allah upon those who lie. (The Holy Quran, 3:58,59 and 60 )
1.Have a bath.
2.Keep fast & give Charity
3.Pray a 2 Raka't Salaat. just before noon time , as under:
In every Raka't, after the recitation of Soorah Al Fatih'ah, recite:
(i) Soorah Al Ikhlaas 10 times.(ii) Aayaat ul Kursee 10 times. (iii) Soorah At Qadr. 10 times.
(iv) After the Salaam go into Sajdah and say 100 times: ALH'AMDULILLAAH SHUKRAN LILLAAH
Then sit and recite the dua'a "Allamumma inni asaloka be anna lakal hamda wahdaka..
Then go into Sajdah and recite :ALHAMDU LILLAH 100 times & SHUKRAN LILLAH 100 times
source : www.sibtayn.com
