Samurah bin Jundub said “The war-cry of the Emigrants was Abdullah and that of the helpers Abd Al Rahman. ”
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues:
The benefit of this is that in darkness or in the case of not having personal acquaintance, there is no mistake in recognizing one's own people.
If a spy or the like infiltrates, it also becomes easier to catch him.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 2595