Life is a journey full of twists and turns. Without a guide in this deceptive path, one can become lost, forfeiting something that cannot be regained - the precious gift of redemption. That is why Islam emphasizes the need for Muslims to never be without a leader. Prophet Mohammad (PBUH&HP) is the best example of a Muslim within Islam.

There has certainly been for you in the Messenger of Allah an excellent pattern for anyone whose hope is in Allah and the Last Day and [who] remembers Allah often. (The Holy Quran 33:21)

O you who have faith! Obey Allah and His Apostle, and do not turn away from him while you hear [him]. (The Holy Quran 8:20)

These Quranic verses firmly establish that no one surpasses Prophet (PBUH&HP) as the ideal role model, guiding us to emulate his actions and lifestyle for our salvation. When we follow someone as a model in our life, we inherently respect his beliefs and ideas. 

From this, we deduce that if our model is devoted to Islam, religion, and the path of Allah's pleasure, we will also try to align ourselves with that path and potentially attain spiritual ascension. Our model here is not an ordinary person but our dear Prophet. Therefore, there is no disputing the goodwill of this revered figure. An important thing that we must learn from the Prophet (PBUH&HP) as the supreme model for Muslims is to know whom to love and whom to dislike.

The question is: how does understanding Prophet’s feelings towards individuals would help us? 
The answer lies in this: “By following the Prophet as an example, we can accurately discern these people, subsequently progressing toward Allah’s satisfaction and eternal happiness.” 

Two figures whom the Prophet constantly favored were Imam Hassan and Imam Hussein (as). Imam Hussein (AS) was born on the third of Sha'ban in the fourth year of AH.

Since the great Prophet passing in the tenth year of AH, Imam Hassan and Imam Hussein (AS) spent their childhood with their dear grandfather.

Before delving further, let us know more about our third Imam. Imam Hussein (as) is also called Aba-Abdillah and Sayyid al-Shuhada among the Shias. He is the third Imam for the Shias, martyred in the course of Ashura. He is the second child of Imam Ali (AS) and Fatemeh Zahra (AS), and the grandson of Prophet Mohammad (PBUH&HP). Following his brother Imam Hassan’s (AS) leadership, he took charge of leading the Shias for ten years. Both Shia and Sunni historical records confirm that the Prophet of Islam (PBUH&HP) announced his martyrdom at his birth and chose the name "Hussein" for him. (1)

The Prophet held deep affection for Imam Hassan and Imam Hussein and recommended everyone to love them. Imam Hussein (AS) is one of the of Prophet’s Ahl al-Bayt and also one of the recipients of the verse of purification*.

Numerous narrations from Prophet Mohammad (PBUH&HP) extol Imam Hussain’s virtue. A famous narration quotes the Prophet (PBUH&HP) on Imam Hussain (AS): “Hussain is from me and I am from Hussain. Allah loves who loves Hussain.” (2)

Through this narration, the Holy Prophet (PBUH&HP) show other Muslims the sacred position of Imam Hussein (PBUH) and imparts the exceptional stature of this lineage. In an era where falsehood and hypocrisy infiltrate the Muslim community, this saying compels believers to rid themselves of hypocrisy and misguidance. 

Regrettably, despite its resonance, this profound message did not deter the brutal martyrdom of Sayyid al-Shuhada (PBUH), which transpired in the Karbala before thousands of seemingly Muslim individuals.

The Prophet’s (PBUH&HP) adoration for Imam Hussein (AS) served a dual purpose: it conveyed not only his love for his grandson, but also aimed to engender affection towards Imam Hussein as the Imam of the Ummah, rallying people to follow him. Therefore, the Holy Prophet of Islam consistently introduced the Imam Ali, Fatima Zahra, Imam Hassan and Imam Hussein (AS) as his family and Ahl al-Bayt. He equated them with the Quran on numerous occasions,  underscoring the necessity for Muslims to accept their leadership and guidance for spiritual elevation. The Prophet also said this in the hadith of the thaqalayn: 

"Indeed, I am leaving two things among you, to which if you hold yourself, you will never astray: the book of Allah –who is almighty and great- and my Ahl al-Bayt (household), my 'itra (family). O people hear! And I have announced to you that indeed you will enter my presence and I will ask you about what you did to the thaqalayn (two weighty things) and the thaqalayn are the book of Allah and my Ahl al-Bayt."(3)

Conclusion: 

These narrations illuminate Imam Hussein’s (AS) lofty status in the the Prophet’s (PBUH&HP)eyes and the Prophet’s responses to him serves as a guide. Not only are Muslims, as followers of the Holy Prophet, must praise and love Imam Hussein, but we must also adopt his behavior, thoughts, and ethics, and follow his path in our lives. Furthermore, the Prophet's interactions with Imam Hussein underscore that those who harbor hostility or animosity towards him today are not true Muslims. This group should not be regarded as part  of the Prophet’s (PBUH&HP) religion.

References:

1.  Al‑Irshad (2nd Volume - page 130)
2.  Sunan al-Termizi (6th volume – number 3775)
3.  Al-Kafi (1st Volume – page 452)

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*The Verse of Purification is the 33rd verse of Al-Aḥzāb in the Quran (33:33). The verse has special importance for Shia Muslims due to giving information about Ahl al-Bayt of Prophet Muhammad (PBUH&HP). Shias reportedly believe it to designate the "Ahl al-Bayt" being infallible.

After Imam Ali (AS) was martyred, Imam Hassan (AS) took over as his successor who like his father fought against Mu’aviah but he couldn’t defeat him because his army was not sufficiently loyal. His reliable followers were inadequate and he feared that they could be killed in the battle. Thus, Imam Hassan (AS) made a peace treaty with Mu’aviah, under the duress against his own will. 

Mu’aviah became the Caliph under specific circumstances. For instance, he wasn’t allowed to choose the next Caliph and his son (Yazid) couldn’t be his successor. On the other hand, when Mu’aviah died, Imam Hussain (AS) was opposed to and fought against Yazid and he and his followers were brutally martyred. Both Imam Hassan (AS) and Imam Hussain (AS) had few collaborators/ associates/ helpers; however, this did not stop him from protesting against Yazid and his tyranny. 

One of the most controversial questions about Imam Hussain (AS) is that why he did not make peace with Yazid just like his bother did with Mu’aviah? 

The Wrong Belief

It is worth noting that it would be so irrational to think that Imam Hussain (AS) had a different disposition from Imam Hassan (AS), for example one was more of a diplomat while the other was more of a fighter. In fact the objective conditions at the times of two Imams were rather different hence, their approach apparently differed. 

1.    Mu’aviah was willing to make peace with Imam Hassan (AS) but Yazid wasn’t like his father. Mu’aviah did not want to fight against either Imam Hassan (AS) or Imam Hussain (AS) and they were not prepared to do so. Once the governor of Medina wrote to Mu’aviah that Hussain (AS) does not want to take over the kingdom for now but he may do in the future. Mu’avia wrote to the ruler:
Leave Hussain (AS) and do not bother him because we don’t want to conflict with him while he is in peace with us (1)

On the other hand, when Yazid became the Caliph, he ordered the  governor of Medina to make Imam Hussain (AS) to either obtain the oath of loyalty (to the Caliphate of Yazid) or failing that, kill Imam Hussain (AS), cut off his head and send it to Yazid.

2.    In public Mu’aviah was, at least superficially, a pious person who would not commit sins or harm innocent people. Sometimes even the followers of Imam Ali (AS) had doubts about the impiety of Mu’aviah. While Yazid had no reservations, he would commit sins in public including drinking wine, playing with dogs and monkeys and etc. As in  this regard Imam Hussain (AS) said:
Yazid is an alcoholic person and kills innocent people and does sins in public, so a person like me wouldn’t accept a person like him as their king (2)

3.    Mu’aviah was a very powerful king with strong army but Yazid was not as clever and strong.

4.    The loyalty of many of Imam Hassan’s (AS) followers was questionable.   Some abandoned him and some others tried to kill him or even surrender him to Mu’aviah. But the companions of Imam Hussain (AS), as he himself said, were of a better and more loyal caliber. (3)

5.    Mu’aviah was among the companions of the Prophet (PBUH) which earned him the respect of Muslims in general whereas Yazid was not a companion of the Prophet (PBUH) was so important to Muslims in that time and people would respect him so much. But Yazid wasn’t a companion of the Prophet. 

6.     Mu’aviah’s sister (Um Habibah) was the Prophet’s wife. Since the prophet’s wives are called ‘’the mothers of the believers ‘’; therefore, Mu’aviah was called “the uncle of the believers”. Yazid, however, did not have such status.

7.    Although he did not meet any of his commitments that he had already made, Mu’aviah could say that he is legally the caliph because of the peace agreement between him and Imam Hassan (AS) because Yazid could not claim such legitimately. 

Imam Hussain (AS) and respect to the Peace

Some people think that Imam Hussain (AS) didn’t agree with his brother in making peace with Mu’aviah however because of his respect for his brother, he observed the peace treaty and did not oppose Muaviah. However, this view about Imam Hussain is not right.

If we assume/Supposing that Imam Hussain (AS) did not actually agree with his senior brother, he could fight against Mu’aviah; because, the latter broke his agreement that he had made with Imam Hassan (AS), when he made his son, Yazid, his successor and Imam Hussain (AS) had no agreement with Muaviah however the circumstances of Imam Hussain were unsuitable for an uprising against Muaviah.

References 

1.  Bihar al-anvar, Majlesi, vol.44, pg.212
2.  Maghtal al-Hussain (AS), Abd ar-Razzaq al-Muqarram, pg.129
3. Musnad al-Imam ash-Shahid, al-Atarodi, vol.2, pg.4