The ‘Dark Thursday’ or the ‘Calamity of Thursday’ was a turning point in the history of Islam as this widely documented incident shows:
Saeed Ibn Jubair reports:
It was the 11th Hijri in the final days of Holy Prophet (s.a.w.a.) when Ibn Abbas was heard saying:
Thursday! And you know not what Thursday is? After that Ibn Abbas wept till the stones on the ground were soaked with his tears.
On that I asked Ibn Abbas: What is (about) Thursday?
He said: When the health of Allah’s Messenger (s.a.w.a.) deteriorated, he ordered: Bring me a bone of scapula (pen), so that I may write something for you after which you will never go astray.
But the people differed in their opinions although it was improper to differ in front of a prophet.
They said: What is wrong with him? Do you think he is delirious (Allah forbid)? Ask him (to understand).
The Prophet (s.a.w.a.) replied: Leave me as I am in a better state than what you are asking me to do.
Sahih Bukhari book 58 trad 10
What is it that the Prophet (s.a.w.a.) wanted to write on that day?
Clearly the Prophet (s.a.w.a.) was going to write something on that day that would have made some companions very uncomfortable. It did not take long for the truth of the matter to come out.
Ibn Abbas narrates:
Umar confessed to me: In his final illness Allah’s Messenger (s.a.w.a.) had decided to appoint Ali (a.s.) as his successor but I prevented him.
Sharh Nahj al-Balaghah v 12 p 21
Indeed, the Calamity of Thursday forever left the Muslims in a state of confusion and perplexity with regards leadership. Had the Prophet (s.a.w.a.) been allowed to nominate Ameerul Momineen – Ali Ibn Abi Talib (a.s.) in his final illness, after formally announcing his caliphate in Ghadeer only a few weeks earlier, Muslims could have availed of the sweet water of divine guidance, rather than the dirty water they have been drinking for 1,400 years.