In Sermon (156), Imam Ali (a.s.) discusses the mission of Prophet Muhammad (peace be upon him) and the oppressions of Banu Umayyah. This sermon was delivered at a time when the Islamic community was facing various challenges, particularly during the rule of Banu Umayyah. Imam Ali emphasized that the Prophet's mission was a crucial turning point, occurring when the chain of messengers had ceased and people had drifted away from religion.

The Imam stated that the Prophet (peace be upon him) came with the Quran, which confirms previous scriptures and serves as a guiding light for humanity. The Quran contains accounts of the past, prophecies about the future, and guidance for improving human relationships. This message is a comprehensive guide for humanity, retaining its significance across ages.

Another important point in this sermon is the Imam's critique of the incompetence and oppression of Banu Umayyah. He pointed out that those unworthy of the caliphate were appointed to leadership positions. The Imam warned of Allah's impending punishment, stating that these oppressors would face retribution for their actions.

Imam Ali (a.s.) used a powerful metaphor, asserting that Banu Umayyah would have to spit out the caliphate like phlegm. This serves as a compelling reminder that tyrants meet a dire end and that everyone will be accountable in the court of Allah. The sermon teaches us the importance of choosing the right leadership and raising our voices against oppression.

This sermon reminds us of the necessity to uphold religious and moral values, and the need to support the truth in every era. The words of Imam Ali (a.s.) continue to serve as a guiding light for us today.