In the event of Karbala on the shoulder of Imam Hussein (PBUH) an ulcer-like effect was found. Hazrat Imam Sajjad (peace be upon him) was asked about it. He said: this sign is due to the leather bag which was full of supplies for widows, orphans and the poor and was carried by Imam Hussein (peace be upon him) to them.
Imam Hussein (PBUH) says: certainly, the indigents requests from you is blessings from Allah Almighty, So do not get tired of blessings for they may turn into punishment.
source : erfan.ir