Abdul A’ala ibn e A’in of Kufa was preparing to go to Medina to visit Imam Jafar al-Sadiq (‘a). The followers of the Ahl al Bayt (‘a) thought it was a good opportunity to get answers to the questions that cropped up every now and then, and confused them. They all wrote down their questions and handed them to him. However, they added, ‘Ask Imam Jafar al-Sadiq (‘a) to let us know orally, what the duties of a Muslim are towards his Muslim brethren.’
Ibn e A’in reached Medina and went straight to the Imam (‘a). After the initial courtesies were over, he presented the written questions to him and added the one asked orally by the people of Kufa. The Imam answered all the questions but did not respond to the oral one..
Many days passed, but no one referred to the question that remained unanswered. Finally Ibn e A’in decided to return home, so he came to bid the Imam (‘a) farewell. Before leaving, he said, ‘Ya ibn e Rasool Allah, I have received all the answers but one. Now that I’m leaving, I’d be grateful if you gave me the answer to that one, so that I might be able to satisfy the thirst for knowledge of those who asked it.’
‘I intentionally avoided answering it,’ replied the Imam (‘a)… ‘Why, I beg of you?’ ‘Because if I tell you and you do not act according to the information you receive, you will be excommunicated from Islam.’‘
He then informed him of three basic duties of a Muslim towards his brethren-in-faith ‘Remember, these three divine commands and never treat them lightly
Firstly, be just in all affairs among yourselves and treat one other as you would like to be treated yourself by others
Secondly, never think twice about helping your brother-in need with your resources; do it at once, lest your self-interest intervenes.
Lastly, following the above two will become easy if you always remember the Lord under all circumstances. This does not mean repeating Alhamdolillah, Subhan Allah all the time on the rosary. It means a constant awareness of His presence, which prevents you from committing a forbidden act. Society would face fewer problems if everyone was convinced that he was being watched.’
Reference : Anecdotes of The Ahlul Bayt (Daastaan e Raastaan ) by Ayatullah Murtadha Mutahhari