What can be said about the worship of the one who was brought up in the laps of the Messenger of Allah (saaw) and Imam Ali (a.s), and had benefited from their company. Imam Hussain (a.s) was fond of worship since his early childhood. He often used to pray with the Messenger of Allah (saaw). Hafas bin Ghayas reports that one day the Messenger of Allah (saaw) stood up to pray and Imam Hussain (a.s) also came and stood besides him. When the Messenger of Allah (saaw) recited the Takbir (Allaho Akbar), Imam Hussain (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 (saaw) repeated the Takbir. But again it didn't come out perfectly from Imam Hussain (a.s). Thus the Messenger of Allah (saaw) had to recite the Takbir seven times altogether. Therefore since that time it became a Sunnat (recommended act) to recite seven Takbirs before Takbiratul Ehram (Allaho 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 rakats (units) of prayers every night," Imam Hussain (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 Ibn 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 Hussain (a.s) could have performed such worship. The most difficult was the time of the noon prayers. The opponents were showering arrows and Imam Hussain (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:

1. Book named "Akhlaq al-A’imma, Morals & Manners of the Holy Imams" by author Maulana Sayyid Zafar Hasan Amrohi.

2. Al-islam.org (https://www.al-islam.org/akhlaq-al-aimma-morals-manners-holy-imams-maulana-sayyid-zafar-hasan-amrohi)