The Holy Prophet (s) gave Imam Ali (‘a) 12 dirhams to purchase a long shirt for him. Imam Ali (‘a) bought a shirt and gave it to him (s). The Holy Prophet (s) asked, ‘How much did it cost?’ ‘Twelve dirhams.’
‘I am afraid I wouldn’t like to wear something so expensive. If the shopkeeper agrees could you return it and buy something cheaper?’ ‘I’ll see, Ya Rasool Allah.’
Imam Ali (‘a) spoke to the shopkeeper and he agreed to return the money and keep the shirt. Then both (s) went towards the market together. On the way, they saw a young slave-girl sitting in a corner of the street and crying. The Holy Prophet (s) went to her and asked affectionately, ‘Why are you crying?’
‘My master gave me four dirhams to fetch goods from the market. I have lost them and can’t find them. I don’t have the courage to go home.’
The Holy Prophet (s) gave her four dirhams and told her to buy the needful and go home. He then went to a shop and bought a shirt for four dirhams, and wore it. On the way home, a man, totally nude, was seen. Quickly, the Holy Prophet (s) took off his shirt and made him wear it. He (s) then went back to the shop and bought himself another shirt for four dirhams. On the way back, he found the slave-girl sitting with all the goods and nervously looking around.
The Holy Prophet (s) asked, ‘Why have you not gone home?’ ‘I am afraid to go home because my master will ask me why I took so long and might beat me.’ ‘Give me your address. I shall accompany you so that no one says anything to you.’ They reached the place and the girl stopped, pointing to the house where she lived. The Holy Prophet (s) went close to the door and said loudly, ‘ Assalam o Alaikum, dwellers of this home.’
There was no answer. He (s) repeated the greeting again but was met with silence. The third time, the inmates all replied in unison, ‘Assalam o alaikum wa rahmatullah e wa barakatahu, Ya Rasool Allah.’
‘Why did you not respond the first time? Did you not hear my voice the first two times? ‘We heard and recognized your voice the very first time.’ ‘Then why did you not respond?’ ‘Your greetings bring blessings with them, Ya Rasool Allah. We wanted to gain as many as we could.’
‘I have come to ask you to excuse your slave-girl for being late, and not punish her.’ ‘Your coming is such a blessing for us that I release her from bondage this instant.’ The Holy Prophet (s) looked at Imam Ali (‘a) and smiled, ‘Alhamdolillah! These 12 dirhams were so blessed, that they clothed two bodies and freed one slave-girl.’
Reference : Anecdotes of The Ahlul Bayt (Daastaan e Raastaan ) by Ayatullah Murtadha Mutahhari