Considering the high status of the household of the Prophet (s) and the position of Alavids adherents of Imam Ali ('a) and the household of the Prophet (s) in Medina, it is necessary to shed light on their stance as well as their role during the course of Medinans uprising and their revolt against the Umayyid rule.
The importance of this issue is obvious to any researcher of the history of Islam who has studied and analyzed the tragedy of Harrah, or is going to do so. Particular reference to the time of this event from a trans-historical and religious aspect should be kept in mind.
The tragedy of Harrah and Imam Zayn al-'Abidīn's ('a) stance toward it is significantly beyond just a historical research for the followers and adherents of the Prophet (s) and His Ahl al-Bayt ('a), as the Imam's negative or positive or even indifferent reaction towards such affairs would on one hand be a religious frame of reference to them, and on the other hand, can be used as a basis for political and legal opinions in their religious and social life.
What we have said so far about the regretful tragedy of Harrah is a documented historical look at the authentic reports that the historians have recorded. However, a study of the role and position of Imam Zayn al-'Abidīn ('a) in the protest rallies of the people of Medina against the Umayyid's rule is possible from two different aspects.
   A merely historical outlook
   A religious and ideological view

A. Historical Glance at Imam Zayn al-‘Abidīn’s (‘a) Position
If historical accounts about a personality or event merely narrate a report without special analysis and evidence-based judgment, it can take the form of short and scattered remarks about the past and ignore the peripheral issues and the specific conditions relating to time and location. However, if alongside, it also makes judgments and assessments, it would require mentioning of the relevant past records and their backgrounds.
What is recorded in the historical sources in the form of brief narrations reveals that Imam Zayn al-'Abidīn ('a) did not have an active and encouraging presence in Medinans' uprising and revolt. Rather, he had left Medina in order not to witness the imminent tragedy there.
The fact that in the historical and traditional sources there is no statement by Imam Zayn al-'Abidīn ('a) that implies the encouragement of Medinans to resist against the Syrian army or preventing them from revolt indicates that the Imam ('a) had not been able or had regarded as advisable to interfere in this event. But why indeed?
Did Imam Zayn al-'Abidīn ('a) not hold the required social position, after the tragedy of Karbala and the killing of majority of adherents of Imam Ali ('a) and the followers of Ahl al-Bayt ('a), to involve in the incident and viewed as futile to command the people of Medina to guide them to good and prohibit them from evil?
Was the revolt of the inhabitants of Medina only religiously motivated or was it considered as a combination of religious, political, tribal, and economical motivations? Or, why could not the interference of such spiritual figure as Imam Zayn al-'Abidīn ('a) in such complicated and multifaceted event be crucial and effective enough to be accepted and welcomed by the major trends of the time?
Was now Imam Zayn al-'Abidīn ('a) taking upon himself as his legal and social obligation to help out or prevent the Muhājirin and the Ansār, the reciters of Qur'an, the narrators of hadīth, and the companions of the Prophet (s) from the battle, that is those who, as he witnessed at close quarters to himself, with all their high status and position never assisted his grandfather 'Alī, his uncle Hasan b. 'Alī ('a), or his father Imam Husayn b. 'Alī ('a) and depended on their own understanding and knowledge in ups and downs of the incidents rather than on the Ahl al-Bayt ('a)? Or else, he did not feel obliged to accompany them due to the weakness of this movement, or did not prevent them because of their inadvisablity?
Was Imam Zayn al-'Abidīn ('a) entangled in a political and social seclusion and pursuing monasticism? Or did he not have the morale for getting up again into conflict with the Umayyid ruling system? Or did he firmly decide not to fight against the corruption of the rulers and their tyranny like the manner and lifestyle (sīra) of his grandfather 'Alī b. Abī Tālib ('a), his uncle Hasan b. 'Alī ('a), and his father Husayn b. 'Alī ('a)?!
Once the historian wants to step into research and analysis and then make a judgment about the interference and non-interference of Imam Zayn al-'Abidīn ('a) in the tragedy of Harrah, he would be facing all the above questions and should have answers to all of them, presenting authentic reasons for every view he adopts.
The simplest analysis is to regard the Imam's ('a) silence as his impartiality in this event and view that impartiality as a result of his abandoning duty and path of martyrdom and resistance, and his compromise with the rules in order to survive. But such an analysis would be made by an ignorant and biased person, as the past personality traits of Imam Zayn al-'Abidīn ('a) does not validate such an analysis. Despite his exhausted body due to the wounds from the heavy chains fastened to his body and although being surrounded by Yazīd's troops and supporters and in a land where 'Alī ('a) has always been cursed, he stood up before the arrogant Umayyid ruler and cried out:
“O Yazīd! Are you threatening me to murder?! Have you not learned the fact that being killed in the way of the Truth is an eternal success and a tradition among us and martyrdom is a dignity for us?!”
Did the Imam ('a) not utter these words after the tragedy of Karbalā; was he not carrying the deep wounds of the memory of 'Ashūrā on his body and soul when he expressed himself so courageously?!
Was it by any means possible that such a free-spirited, brave, and noble figure would give up all those highly influencing and chrished memories within several months and come to compromise and lip-service with the murderers of his father and their accomplices and become indifferent to their defeat and destruction?!
Was it not the case that whenever the eyes of his holiness were cast on fresh water, he would weep to keep alive the memory of the severe thirst of the martyrs of Karbalā and the tyrannies they suffered and the gravity of the crimes committed by the Umayyids, leaving deep impact on the souls and emotions?
Was he not the one who in his supplications would breathe the love of the Prophet's (s) descendents into the souls and hearts of the monotheists, and this way would trouble the Umayyid's slumber? Was he not the one whose brilliant thoughts and steadfast personality inspired such great warriors as Zayd b. 'Alī b. al-Husayn and Yahyā b. Zayd who bravely fought against Umayyid injustice and oppression? And from among his progeny such Imams and leaders were born who never compromised with the oppressive powers, used every opportunity to expose the real face of the tyrants, and were all killed as martyrs?
If the historians and analyzers of this historical event take into consideration all these facts together in an integrated way and all the aspects, they will not accept the naïve statements and the opportunistic reports of those unfamiliar with the school of divine leadership (Wilāyat).
Thus, if Imam Zayn al-'Abidīn ('a) did not go along with the uprising of Medina, it has been because:
Firstly, he had identified various goals and motives among the people of Medina all of which were not religious.
Secondly, the Imam ('a) did not see the condition as appropriate for confronting the Umayyid government and considered the revolt of the people of Medina as paving the way for massive bloodshed and transgression upon the chastity of Muslim women. This was in the same way as his noble father, Husayn ('a), left Medina during the night, it was because he did not want his blood to be shed in the Sanctuary of the Holy Prophet (s) and so his martyrdom took place in a situation that would convey the everlasting message to the subsequent generation.
Thirdly, if he prevented people from uprising honestly and outrightly, it would so happen that the people would take the Imam's words as a result of his past disappointment of fighting against Yazīd! Nevertheless, Imam Zayn al-'Abidīn ('a) practically showed the people of Medina and those who were mindful of the Imam's viewpoints and obedient to him that they should not get involved in this course of events.
Fourthly, the method of fighting adopted by the inhabitants of Medina against the Syrian army was predicted to be inefficient; for, although in the battle of Ahzāb, the Muslims utilized a similar method and triumphed in the early stage, the circumstances had changed over time. In the tragedy of Harrah, the people of Medina neither enjoyed the empathy and coordination of the Prophet's (s) time, nor had a leader like the Prophet (s).
In addition to the above, the presence of the women and children in Medina had a very important impact leading to the defeat of their uprising, as the combatants had to abandon the battlefront and go back to town for the fear of the Syrians' invasion of their houses.
Thus, Imam Zayn al-'Abidīn ('a) had practically warned against this critical event and demonstrated to the inhabitants by having his family and relatives taken away from Medina and transferred to the region of Yanbu'[1].
In conclusion, the position that Imam Zayn al-'Abidīn ('a) practically adopted was very well calculated and in the light of the above-mentioned considerations, the most logical one, since, in a short while, this reality was to be revealed to the inhabitants of Medina.

B. An Ideological Glance at Imam Zayn al-‘Abidīn’s (‘a) Position
What we said so far was merely a historical look based on human calculations that could be noticed by any researcher and thinker; whereas, the interference or non-interference of Imam Zayn al-'Abidīn ('a) in the process of Medinans' uprising has a religious perspective, too, which is significant to the Shias and the believers in the spiritual status of the Imams and the infallibility of the Ahl al-Bayt ('a).
In this view, the Imam is not a simple decision maker who takes actions according to his personal information and experiences. Rather, he is committed to an obligation that God has explicitly appointed him for and other people have to obey him, take his words and actions as criteria for their beliefs and behavior, and do not seek precedence over him in thought and practice.
From this perspective, Imam Zayn al-'Abidīn ('a) had acted according to a superhuman obligation, and those of the Medinans, who due to their lack of belief in Wilāyat and Imamate (divine leadership of the Imams among Ahl al-Bayt - 'a) or for any other reasons stepped into this uprising, suffered great loss.
Here, the question arises that whether the Medinans' uprising was rightful and their killed ones can be regarded as martyrs, or their uprising had been a rebellion and revolt against an Islamic ruler?

Reference
1. Yāqūt Hamawī, Mu‘jam al-Buldān, vol. 5, p. 449.