A video released by the group on one of its affiliated websites showed dozens of local Somalis lining up to report the number of heads of livestock they had in their possession so that the amount that they should pay in zakat could be determined.
The footage also showed a number of poor Somalis receiving their share of the zakat and praising Al-Shabaab for the charitable gesture.
An Al-Shabaab leader, identified as Abu Mohamed, showed in the video saying that alms had been distributed among the poor after having been collected from the rich.
He said the zakat system was followed in all Al-Shabaab-held areas, including Middle Juba in the south, Gedo in the southwest, and Hiran in central Somalia.
Zakat is one of the Islamic faith's "five pillars," according to which every able-bodied believer should pay 2.5 percent of their wealth every year to the poor.
Although Al-Shabaab was ejected from Mogadishu by African peacekeepers and the Somali army, the group has continued to target government officials and foreign troops deployed in the city.
Somalia has remained in the grip of on-again, off-again violence since the outbreak of civil war in 1991.
Earlier this year, Somalia had appeared to inch closer to stability after government troops and African Union forces – deployed in the country since 2007 – drove Al-Shabaab from most of its strongholds.