Thus when we address Abi ‘Abdillah and say “As-Salamu Alaika...
Thus when we address Abi ‘Abdillah and say “As-Salamu Alaika Yaa Aba ‘Abdillah” we are saying that: ‘May the peace and tranquillity which Allah bestows upon His creations also be showered upon you. Truly, we submit to your mission and commandments and whatever you ask us to do. In addition, we shall not do a single thing to hurt you – either your physical presence or more importantly, your feelings.
In actuality, we are promising the Imam that we shall not break the laws of Allah (since our Imam grieves when he sees us doing this) nor will we do anything to trample on the sacred goals and objectives which he laid down his life to protect. Literally, Abillah means the ‘worshipper of Allah’ and the literal meaning of Aba ‘Abdillah is the ‘father of the worshipper of Allah’.
The custom of the Arabs was that if a person possessed a specific characteristic, they would then refer to him as the ‘father’ of that trait. Thus we see that Abu Jahl was known as such not because his son was Jahl (ignorant) or named Jahl, rather it was due to the fact that he best personified ignorance and it can be said that he was the “father (leader)” of ignorance!
Similarly, one who had a strong love and affection for cats would be referred to as Abu Hurairah – not that he is the father of a cat, rather, since he loved and liked to play with cats he developed this title!
Thus, had Imam Husayn (peace be upon him) not risen and sacrificed his life on the plains of Karbala’, today Allah would not have been worshipped as He should be – the Shariah of Muhammad would have been replaced with the Shariah of Yazid and his likes – thus, none of us would have been worthy of the name ‘Abillah’. With the murder of Imam Husayn, he gave life to the title ‘Abillah’ and ensured that we could worship Allah as He has required us to.
Thus for this reason too, he is known as the ‘father of the worshipper of Allah’. Therefore, any person who is blessed to be able to worship and submit to Allah has been given this blessing through the blood of the 3rd Imam.