What can be said about the worship of the one who was brought up in the laps of the Messenger of Allah (P.B.U.H&H.P) and Imam Ali (A.S), and had benefited from their company. Imam Hussein (A.S) was fond of worship since his early childhood. He often used to pray with the Messenger of Allah (P.B.U.H&H.P). Hafas bin Ghayas reports that one day the Messenger of Allah (P.B.U.H&H.P) stood up to pray and Imam Husain (A.S) also came and stood beside him. When the Messenger of Allah (P.B.U.H&H.P) recited the Takbir (Allah-o-Akbar), Imam Hussein (A.S) who was aged five or six at that time also tried to recite it but could not do so properly. The Messenger of Allah (P.B.U.H&H.P) repeated the Takbir. But again it didn't come out perfectly from Imam Hussein (A.S). Thus the Messenger of Allah (P.B.U.H&H.P) had to recite the Takbir seven times altogether. Therefore since that time it became a recommended act (Sunnat) to recite seven Takbirs before Takbirat-ul-Ehram (Allah-o-Akbar at the beginning of Prayers).
Someone asked Imam Zainul Abideen (A.S) why his respected father had so few children. He replied, "The reason is that he used to recite one thousand units (rakats) of prayers every night," Imam Hussein (A.S) also performed twenty-five Hajj pilgrimages on foot though his vehicles used to remain with him during the journeys.
He was so much fond of the worship of Allah that on the eve of Ashura he obtained respite with a lot of difficulty from Umar Ibne Saad. Such a difficult night the eve of Ashura was that all the calamities had surrounded the Imam (A.S) even then he was engrossed in prayers and devotions all night long with utmost sincerity, humility and devotion. Only a person like Imam Hussein (A.S) could have performed such worship. The most difficult was the time of the noon prayers. The opponents were showering arrows and Imam Hussein (A.S) was performing the prayers. More significant was the time of the afternoon (Asr) prayers. A wounded and oppressed creature was surrounded by the enemies who attacked him from all sides while he performed his Asr prayers in gestures. The climax was that they beheaded him while he was in prostration.
source : sibtayn