Merits of Imam Hussein (a.s):
 These traditions were related from Ibn Athir’s book entitled, Usudul Ghabah.

 A man asked Abdullah bin Umar:  "What will be the position if the blood of a mosquito touches the dress of a man?"  Abdullah ibn Umar said:  "Look here!"  This Iraqi inquires about the blood of a mosquito, although these very Iraqis killed the son of the Prophet saying:  "Hasan and Hussein are my two fragrant flowers in the world".

 The Holy Prophet (s.a.w.) said:  "Hussein is from me and I am from Hussein.  Allah loves him who loves Hussein.  Hussein is the son of the Prophet and father of the Imams".
 Anas bin Harth Kahili, and his father who were the companions of the Holy Prophet, says that he heard the Holy Prophet saying:  "This very son of mine will be killed at a place in the region of Iraq.  Whoever is present at that time and is in a position to assist him should assist him".

 The prelude to what had been said by the Holy Prophet became apparent in 60 A.H. and Imam Hussein also got ready to meet martyrdom.  However, it was not, as some people have imagined, that, as there was no chance of his escaping death, and he knew that even if he surrendered he would be killed, he became helpless and exposed himself to martyrdom.  In fact this was not the position, and whoever says or writes this says something flabby and baseless.  If that had been the case what value would there have been of the Imam’s action and how could the world attach all this importance to this sacred rising?  This movement is the central point of all the sacred movements of the history of Islam and is in fact the center of all sacred religious movements, whether they were initiated before Imam Hussein or were led after him by Zayd bin Ali, Hussein ibn Zayd, Sahib Nafs Zakiyya and his brother Ibrahim, Hussein Shahid Fakh and others.  How is it possible that such a movement should be analyzed with such baseless explanations?
 The correct position is the same as the end of 60 A.H. and in the beginning of 61 A.H.

Imam Hussein felt that the Islamic Society had reached a stage of spiritual and moral degradation which could not be reformed except by means of rising and martyrdom.  It does not, however, mean that it was not possible for him to continue to live  and he, therefore, chose to be martyred.  What is meant is that he could not find any prospect for the existence of religion and the Islamic ummah except by means of sacred revolution.  He concluded that if he wanted the Muslim ummah to live, and there should be a Muslim ummah in the world, he himself must be sacrificed and his dear ones like Zaynab, Umme Kulthum, Fatima Bintul Hussein, who were the greatest and the most eloquent orators of the world of Islam should continue Imam Hussein’s mission by inviting the attention of the Muslim ummah to its shameful condition, in the bazaars of Iraq and Syria, deliver the Muslim ummah permanently from the danger of death and annihilation, keep alive the sacred movements which were started before Hussein bin Ali and open a smooth path for the future religious movements of the Muslims.

Lessons from Imam Hussein (a.s.)
1. It shows the state of Muslim society during and after Muawiyah's twenty-year rule, a matter which prompts every concerned Muslim to study and investigate how it came to prevail in the not too long a period, a single generation or nearly fifty years, after the demise of the Noble Messenger (S).

2. It shows the state of the common people, especially the society's poor and weak, who lived in complete neglect on the part of the rulers, contrary to the Prophet's practice and his great concern for their welfare and rights.

3. It shows the people's indifference in regard to the Prophet's Ahlul-Bayt(A) and their obviousness to the Prophet's earnest and oft-repeated advice and persuasions ( so repetitive that they fill the hadith corpus, sunni and Shii; [ see the article on Hadith al-Thaqalayn in Al-Tawhid Vol. Viii No.1 ] ) regarding them . It was this general indifference towards the Ahl-ul Bayt ( A) and the common ignorance regarding their sublime station in Islam that emboldened a profligate like Yazid to kill the Prophet's only living grandson in such a barbaric manner and to imprison the women and children of his
noble family. History shows that this indifference had causes that lay in the past.

4. Had it not been for the heroic struggle of al-'Imam al-Hussein (A), nothing would have remained of the genuine teachings of Islam. even Yazid, with the help of hired historians, would have gone into history as a respectable Islamic ruler and as a deserving successor of the Messenger of Allah (S). Of course, some court historians and fuqaha tried to justify even the blackest crimes of Yazid as errors of ijtahad. But such justifications did not succeed in convincing honorable or aware Muslim. All that such historians and fuqaha could succeed in achieving was everlasting ignominy for themselves.

Al-Imam al-Hussein ( A) through his tragic martyrdom revived Islam and preserved its authentic teachings from the hands of tyrants. hence the Islamic world is indebted to this brave son of Fatimah al-Zahra ( A) and shall remain indebted to him to the Day of Resurrection.
 

Reference: Know Your Islam.