Charity During Prayer
One day a beggar came into a mosque and went around asking people for money but no body gave him anything. Imam ali was praying and in the state of kneeling before Allah and he pointed out his ring to the beggar who removed it from his finger.
The Prophet saw this beautiful act of Ali giving charity while he was praying and he prayed to Allah to strengthen him with Ali and support him in the task of guiding the people towards Islam.
Just then the trustworthy angel Gabriel appeared before Prophet Mohammad and told with the following words from Allah:
بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ
" Certainly your Master is Allah and His Messenger and those who believe who establish prayer and give charity while they bow. And who ever takes Allah and His Messenger and those who believe as a guardian, so surely the party of Allah will be victorious."
Allah (swt) answered the prayer of Prophet Mohammad through these words because he sets apart himself, Prophet Mohammad and Imam Ali as the masters of the believers.
This incident of Imam Ali giving charity while he was praying was so important because no one could argue that the verse could be talking about anyone else. Allah spoke about Imam Ali in a plural sense to highlight Imam Ali's importance which is bigger than that of any single person.