My sincere condolences to the Imam (ajtf) of our time and to Muslims everywhere on the martyrdom anniversary of Imam Hasan al-Mujtaba (as). There is a difference of opinion amongst scholars on the day of his actual demise – some suggesting the 7th of Safar while others have even mentioned the 25th of Rabi al-Awal and 28th of Safar. Nevertheless, it is accepted that the Imam was poisoned by his wife, who was bribed by Muawiyah.
I was reading up a bit more on his wife, Ja’dah, and found this excerpt in the book on the Life of Imam Hasan al-Mujtaba which I found very interesting. The real intent was to marry the daughter of a man by the name of Sa’eed, who was however fooled by Ash’ath into marrying his daughter to a cousin of hers. Ash’ath then came to Imam Ali (as) and conveyed him about what Sa’eed had done and offered his daughter instead (who Imam Hassan (as) ended up marrying).
The historians have differed over her name. It was said that her name was Sukayna, and was said Sha‘tha’, and was said A’isha. The correct name is Ja’dah, as most of historians have mentioned. As for the reason that Imam al-Hasan married her, it was that Imam Ali (a.s), asked Sa‘eed bin Qays al-Hamadani for his daughter’s hand (Umm ‘Uran) and wanted to marry her to his son al-Hasan. Sa‘eed said to him: “O Commander of the faithful, give me a time that I may consult (her mother).” Then he left him. Al-Ash‘ath met Sa‘eed and asked him about his coming, and he told him about the affair. This hypocrite (Ash‘ath) tried to deceive him saying: “How will you marry (your daughter) to al-Hasan while he will pride himself on her, will not treat her with justice and will wrong her? He will say to her: ‘I am the grandson of Allah’s Apostle and son of the Commander of the faithful (Imam Ali), while she does not have such excellence.’ Why do you not marry her to her cousin? She belongs to him, and he belongs to her.”
“Who is he?” asked Sa‘eed?
“Muhammad bin al-Ash‘ath,” replied al-Ash‘ath.
So this stupid (Sa‘eed) was deceived by al-Ash‘ath’s statement and said: “I accept to marry my daughter to him.”
Then al-Ash‘ath quickly went to Imam Ali (a.s), and asked him:
-Have you proposed to Sa‘eed’s daughter (to marry her to) al-Hasan?
-Do you want (another woman) more honorable than her in house, nobler than her in lineage, more beautiful than her, and greater than her in property?
-Who is she?
-Ja’dah, daughter of al-Ash‘th bin Qays.
-We have negotiated with a man. (He meant Sa‘eed al-Hamadani).
-There is no way to the man with whom you have negotiated.
-He had left me to consult her mother
-He had married her to Muhammad bin al-Ash‘ath.
-Before I came to you.
Accordingly, Imam Ali (a.s), agreed on that. When Sa‘eed came to know that al-Ash‘ath had seduced and deceived him, he quickly went to him and said:
-O one-eyed, you have deceived me!
-You are one-eyed and wicked! You wanted to consult (your wife) as to the grandson of Allah’s Apostle, are you not foolish?
Then al-Ash‘ath came quickly to Imam al-Hasan and said to him: “O Abu Muhammad, do you not want to visit your wife?” He was quick in carrying out the affair lest he should miss it. Then he spread carpets from the door of his house to the Imam’s house, and then he carried home his daughter in procession.
 Maqatil al-Talibiyyin, p. 33. Other sources have mentioned that.
 Ibn al-Jawzi, al-Adhkiya’, p. 27.