That was their refusal to join Usamah's army which was personally raised by the Messenger of Allah who ordered them, two days before his demise, to enlist under Usamah's leadership. They went as far as casting doubt about the wisdom of the Messenger of Allah and criticizing him for having appointed a 17-year old young man, who did not even grow a beard, as the army's leader. Abu Bakr and Umar, as well as many other sahaba, refused to join the army in the pretext of taking care of the issue of caliphate despite the Prophet's curse upon all those who would not join Usamah.[14] 

As for Ali and his followers, they were not assigned by the Messenger of Allah to join Usamah's army in order to circumvent dissension, and in order to thus remove the obstacle of the presence of the stubborn ones who opposed Allah's Commandment, so that they might not come back from Mu'ta before Ali was in full control of the reins of government, as Allah and His Messenger wanted him to, as a successor to the Prophet. 

But the shrewd Arabs among Quraysh anticipated the Prophet's plan and refused to get out of Medina. They waited till the Messenger went back to his Lord. It was then that they carried out their own scheme as they had planned, going against what Allah and the Messenger of Allah had willed; in other words, they rejected the Prophet's Sunnah. 

Thus does it become obvious to us, and to all researchers, that Abu Bakr, Umar, Uthman, Abd al-Rahman ibn Awf, and Abu Ubaydah Amir al-Jarrah always refused to be bound by the Prophet's Sunnah, preferring to follow their own views. They always pursued their worldly interests and desired to attain political dominance even if the price of doing so was transgression against Allah and His Messenger. 

As for Ali and the sahaba who followed him, they always upheld the Prophet's Sunnah and acted upon implementing it to the letter as much as they could. We have seen how Ali during that crisis carried out the Prophet's will to give him his funeral bath, prepare the coffin, perform the funeral prayers for him, and to lay him to rest in his grave. Ali carried out all these orders without being diverted by anything even though he knew that the others were racing to Banu Sa`ida's saqeefa (shed) in order to promote one of them as the caliph. He could do the same and sabotage their plan, but his respect for the Prophet's Sunnah, and his implementation thereof, dictated thae he remain by the side of the Prophet. 

Here we have to pause, though for a short while, to observe such great manners which Ali had learned from the Prophet. While sacrificing his position as the caliph in order to carry out the injunctions of the Sunnah, he witnessed the others rejecting the Sunnah as they sought the caliphate.