This is why Ameerul Momineen (as) said...

This is why Ameerul Momineen (as) said, "All the nations were forgiven because of Me. All the nations were destroyed because of Me." This process kept going until it reached RasoolAllah (saw). Because He was the seal of all prophets, He was given the responsibility to deliver the message of the wilayat of Ameerul Momineen (as) to the people until the day of judgment. He officially announced the wilayat of Ameerul Momineen (as).

After RasoolAllah (saw) officially announced the wilayat of Ameerul Momineen (as), Allah declared His religion to be complete and informed the people the beginning and end of religion is wilayat of Ameerul Momineen (as). Wilayat is the key of tawheed. Without it, tawheed ceases to exist. Those who were Muslim in name only and in reality were enemies of Allah completely refused to accept the wilayat of Moula Ali (as), and they waged a war against tawheed.

These people had a psychological disease, and the hatred of Moula Ali (as) was its foundation. Its only treatment was the blood of Imam Hussain (as). This disease kept increasing. It reached its climax on the day of Saqifa. No expert surgeon will operate on a wound until it reaches a point where it is suitable for operation. This is why Ameerul Momineen (as) bore every oppression with great patience and did not take out His sword.

In the war of Siffeen, when the victory was only moments away and Hz Malik ul Ashtar (ra) had reached close to the tent of muawiya (la), Ameerul Momineen (as) called him back. When he came back, he was sobbing intensely. Moula (as) gave him courage and said, "O?Malik! Now it will be decided in Karbala." The reason being this wound was not yet treatable. For the same reason Imam Hasan (as) did not stand against muawiya (la) and kicked the power of government away from Himself.

It was the responsibility of Imam Hussain (as) to operate on this wound. Finally that day which everyone was waiting for came. People?s denials of wahi (revelation), Quran, tawheed (oneness), and their attempts to vanquish the wilayat of Ameerul Momineen (as) had reached their climax. 24 The war of Karbala was fought on the basis of the wilayat of Ali (as).

The proof of this is when anyone would come out of Imam Hussain (as)?s army, he would be chanting this slogan "I am on the religion of Ali (as)". Anyone who would come out from yazid (la)?s army would be chanting "I am on the religion of muawiya (la)". Imam Hussain (as) practically proved wilayat in Karbala.