Islam Guidance

Sahl bin Ahmad narrated from Ali bin Abdullah, from Al-Zubairi Is’haaq bin Ibrahim, from Abdul Razzaq bin Homam, from his father, from Mina, slave of Abdul Rahman bin Awf, from Abdullah bin Masoud, who said:
I was with the Messenger of Allah, when he sighed heavily.
“O the Messenger of Allah, why are you so sad?” I asked.
“O Ibn Masoud, my death is approaching,” the Prophet replied.
“Appoint a successor, O Messenger of Allah,” I said.
“Who?” asked the Prophet.
“Abu Bakr,” I replied.
The Prophet fell silent and sighed heavily again.
“Why you are so sad? May I sacrifice my life for you, O Messenger of Allah” I said.
“My death is approaching,” replied the Prophet.
“Appoint a successor,” I said.
“Who will it be?” asked the Prophet.
“Omar bin Al-Khattab,” I replied.
The Prophet fell silent and sighed heavily for the third time.
“May I sacrifice my mother and father for you. Why are you so sad, O the Messenger of Allah?” I asked.
“My death is approaching,” replied the Prophet.
“Appoint a successor,” I said.
“Who will it be?” asked the Prophet.
“Ali Ibn Abi Taleb,” I said.
Then the Prophet cried and said, “Ah, you people will not obey him! If you would, Allah would allow you (to enter) Paradise. But by disobeying him, Allah will remove the value from anything good that you do.”

[Ghayatol Maram, P 69, H 14.
Khawarezmi in Manaqeb, P 64.
Faraed Al-Semtayn, V 1, P 167, H 209.
Manaqeb Ibn Shahr Ashoub, V 2, P 262.
Bishart Al-Mostafa, P 215.
Tarikh Al-Damesh, V 3, P 72.
Nafahatul Lahout, P 114.
Arjah Al-Mataleb, P 162.
Maqsad Al-Ragheb, P 29.
Majma’ Al-Zawaed. V 5, P 185.
Ibn Katheer in his Tafseer, V 9, P 200.]

Ref: Imam Reza.Network

It all began after the untimely martyrdom of the Messenger of Allah, many of those around the Messenger who had claimed to be his friends, were plotting a major revolution after his demise. As foretold by the Messenger and his master in the Holy
“And Muhammad is no more than a messenger; the messengers have already passed away before him; if then he dies or is killed will you turn back upon your heels? And whoever turns back upon his heels, he will by no means do harm to Allah in the least and Allah will reward the grateful.” (Holy Quran 3:144)
He died, and none of his so called 'dear friends' were next to him, in fact according to the most reliable of his living wives Umm Salama, he died in the arms of his brother and rightful successor the Commander of the Faithful Ali ibn Abi Taleb (A.S). So where were the claimants (ones who claimed to be his closest of friends)? What could possibly be more important than washing and burying the body of Allah’s most loved creation? Unless of course, the Caliphate was more important than this, but if it was then why the Messenger of Allah didn’t choose a successor? But he had, and the people couldn't accept his selection, after all people want someone that follows his whims and allows them to be capricious in nature.
It was Saqifah, that dreaded day, the beginning of all calamities, the mother of all massacres. The day the rightful successor was robbed of his right. This is what allowed Fatima (S.A) to be slapped by Kunfudh and crushed behind the door by the Messenger's own father-in-law!!! It begin there.... It was that incident that allowed all injustices to take place, the murder of the Commander of the Faithful (A.S) in mosque Al Kufa, while he was prostrating, the poisoning of the Grandson of the Messenger of Allah, and the daughter of the first usurper waging war against the Imam of her time and preventing the burial of Imam Hassan to take place next to his Grandfather, in fact she even ordered his purified dead body to be showered with arrows!!! And people like Shimr bin Ziljoshan only emulated the actions of his masters on the day of Ashura, and while Imam Hussain (A.S) was his mother, except that on the day of the incursion of the House of Hazrat Zahra (S.A) only one of her ribs was broken. But on the day of Ashura all of the ribs of Imam Hussain (A.S) were broken!!!!
It all began on that day, when someone asks you when Imam Hussain (A.S) was murdered, you reply it was on the day of Saqifaa!!!

Ref: shiachat.com