The AhlulBayt (s) have been living embodiment of tawheed (belief in the oneness of God). Their every moment of life has been in accordance to the will of Allah (swt). This fact is very much evident in the whole tragic event of Karbala. In Mecca while at Mount Arafat, Imam Husayn’s (as) love and servitude for Allah (swt) became apparent in the famed Dua of Arafat. This prayer our Imam recited on the day of Arafa and it is a lesson for all those who want to understand what tawheed is. Imam’s (as) statement in the prayer that “blind be the eye that cannot see You watching it” signifies his most elevated sense of Allah’s (swt) presence at every place and time.
One often wonders that how a man can bear so much suffering and hardships but he still does not deviate from his faith. How one can witness before his own eyes, his young son dying, small children of his household crying and dying due to thirst, yet remain steadfast? What was the power behind him which only increased as the day of tragedy was unraveling? What did Imam al-Husayn (as) have that was greater than all the sufferings he bore? The answer lies in the same prayer of the day of Arafa which he recited in Mecca: “What can one who misses You find any substitute? What can one who finds You miss anything else? Definitely, failing is he who has accepted anyone other than You as substitute. Definitely, loser is he who have desired for anyone other than You.” Here he proclaims the source of his patience and the source of his contented heart…”What can one who finds You miss anything else?” Imam al-Husayn (as) found His Lord, and so now even all is taken from him including his children, brothers and friends–that all is nothing in comparison to what he found. He found His Lord’s pleasure and that is the biggest substitute for the all loses.
In an age when the Muslim community was being ruled by a tyrant who neither believed in revelation nor in the Prophet (s), Imam’s (as) refusal to submit before the wicked usurping tyrant Yazid (la), saved the message of Islam and revived the spirit of tawheed. Because Imam al-Husayn (as) was the very embodiment of tawheed, the Khwajah Mu’in-al-Din Chishti, a great Indian Sufi of Iranian origin, said
“He gave his life but wouldn’t give his hand in the hand of Yazid (for allegiance)
Verily Husayn is the foundation of la ilaha illa Allah 9there is no God but God)”
On the morning of Ashura, the horsemen of the enemy launched an attack on the ranks of the Imam (as). The Imam raised his hands in prayer and said: “O Lord! I depend on you in every affliction and am hopeful of Your blessing in every hardship. In every difficulty with which I am faced, You are my only remedy and resort. There have been many embarrassments which weakened my heart and no remedy for it was available. The friends did not assist me and the enemies rejoiced at my misfortune. However, when I ceased to seek assistance from everyone except You and sought the remedy only from You, You provided me solace and relief and removed the difficulty. Every blessing and goodness reaches us from You and everything should be sought from You only,” further highlighting the spirit of belief in the oneness of God was alive and well amongst the Bani Hashem at Karbala. 
Some of the Imam’s (as) last words when he was submerged in his blood after being stricken with swords, arrows, spears, and stones, and when his whole body was badly wounded and bleeding, were: “I am pleased with Your decree, obedient to Your command. There is no one worthy of worship but You.” There, Imam al-Husayn (as) in his last moments once more declared his faith in His lord, submitting before His command and will, and being pleased with His will. He became the living exegesis of the following verses of holy Qur’an:
“O soul that art at rest! Return to your Lord, well-pleased (with him), well-pleasing (Him), So enter among My servants, and enter into My garden.” (89:27-30)
After Imam al-Husayn’s martyrdom, members of AhlulBayt (s) were made captives and taken to Kufa in front of Ibn Ziyad (la). There, Ibn Ziyad asked Sayyida Zainab (as), “How have you seen what Allah has done to your AhlulBayt?” She responded, “I have seen Him treating them most beautifully.”  This is the reply from a woman who is in captivity, whose family has been killed. Shiekh Mufid also has mentioned the conversation between Sayyida Zainab (as) and the accursed ibn Ziyad. Ibn Ziyad (la) in his arrogance and wickedness said to Sayyida Zainab (as): “Praise be to God Who has disgraced you, killed you and revealed the false nature of your claims.” She replied to the wicked tyrant in his face as a brave and honored lady: “Praise be to God Who favored us with His Prophet, Muhammad (s), and He has purified us completely from sin. He only disgraces the great sinner and reveals the false nature of the profligate. Such men are not among us, praise be to God.” 
The whole story of AhlulBayt (s) is that of valor and majesty. The source of this lofty majesty and unwavering valor lies in their unwavering faith in Allah (swt). The tyrants committed all acts of aggression and oppression towards the holy AhlulBayt (s) but they could not made them bow and submit before their unholy wishes, because the AhlulBayt(AS) had submitted before the will of Allah, and Karbala was only one example of this embodiment of belief in the Almighty and Majestic.
Peace be upon you, O Aba Abdillah
Peace be upon you, O son of Allah’s Messenger.
Peace be upon you, O choicest of Allah and son of His choicest
O Allah, make me illustrious in Your sight in the name of al-Husayn, peace be upon him, in this world and in the Hereafter
– Ziyarat Ashura
1. A Probe into the History of Ashura’ by Dr. Ibrahim Ayati
2. Islam and the Contemporary Man by Allamah Sayyid Muhammad Husayn at-Tabatabai
3. Maqtal al-Husayn by Abd al Razzaq al-Muqarram
4. Kitab al Irshad by Sheikh al Mufid