Reference: Siffatus-Safwah – Volume 2, Page 96
On the authority of ‘Amru ibn Thaabit who said: When ‘Alee ibn al-Husayn died, they washed him and noticed a black mark on his back, so they (some of them) said:
“What is this?”
So they (the others) said:
“He used to carry a sack of flour on his back during the night and used to distribute it to the poor and needy of the people of Madeenah”.