Sayyidunā Áli Karramallāhu Wajhah was struck on Friday (11th or) 17th of Ramađān, 40 AH when a Kharijite named Ábdu’r Raĥmān ibn Muljam struck him with a poisoned sword at dawn, as Mawlā Áli rađiyallāhu ánhū was proceeding for the Fajr prayer. The blow broke open his crown and the poison reached his brain. Mawlā Áli survived the following two days and he passed away on Sunday night. [Which makes it the 19th of Ramađan]

Ĥasan, Ĥusayn and Ábdullāh ibn Jaáfar gave him the ablution; Ĥasan lead the prayer and he was buried in the night itself in Dār al-Imārah in Kūfā. Ibn Muljam was decapitated and put in a container [qawşarah: pan, vessel]  and was burnt by fire. All of this is reported by Ibn Saád. He did a good thing in that he mentioned these events briefly and in summary without excessive descriptions like some others did. It is also most appropriate because RasūlAllāh şallAllāhu álayhi wa sallam said: ‘When you speak of my companions, withhold [your tongues].’

It is reported in Al-Mustadrak from Suddi that he said: Ábdu’r Raĥmān ibn Muljam was in love with a Kharijite woman named ‘Qaţām’. He married her and [as dower] he gave her three thousand dirhams and promised the assassination of Áli rađiyallāhu ánhū.

Farazdaq refers to this when he says:

fa lam ara mahran sāqahu dhū samāĥatin,
ka mahri qaţāmi min faşīĥin wa aájami
thalātu ālāfin wa ábdin wa qaynatin
wa đarbu áliyyin bi’l ĥusāmi’l musammami
fa lā mahrun aghlā min áliyyin wa in ghalā
wa lā fatku illā dūna fatki’ibni muljamī

I have not seen a dowry [given] by any extravagant man,
Like the dowry of Qatam, among Arabs or Non-Arabs
Three thousand, a slave and a maid
And to strike Áli with a poisoned sword
No dowry can ever be more precious than Áli, and if it did
No murder could have been costlier than the murderous deed of Ibn Muljam

Abū Bakr ibn al-Áyyāsh has said that Áli’s tomb was hidden so that the Kharijites may not exhume it. Shurayk said, that his son, Ĥasan moved his body to Madīnah.

Mubarrad reports from Muĥammad ibn Ĥabīb: The first person whose body was transferred from one tomb to another was Áli rađiyallāhu ánhū.

Ibn Ásākir reports from Saád ibn Ábdu’l Ázīz: ‘When Áli ibn Abū Ţālib rađiyallāhu ánhū was martyred, he was taken to be buried alongside RasūlAllāh şallAllāhu álayhi wa sallam. As they were travelling, the camel on which he was borne ran away in the night and nobody could find it thereafter. He said, ‘It is therefore [some] people of Iraq believe that he is in the clouds.

Someone else has said that they found the camel in Al-Ţayyi’ and he was buried there.

Sayyidunā Áli was sixty three when he was martyred. There have also been reports that he was sixty-four or sixty-five or fifty-seven or fifty-eight.

Tārikh al-Khulafā, As-Suyūţi p.156