You can read this
https://culturalatlas.sbs.com.au/somali-culture/somali-culture-religion
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I don't have any academic sources and It's too late for me to find some. But I'll @ our sspot historians
@Shimbiris @Garaad diinle
I'm not sure on the names of the tribes converted.
Here's some pages from
"Ufahamu: A Journal of African Studies
Title
God, Anti-Colonialism and Drums: Sheikh Uways and the Uwaysiyya " published in 1989
Beginning of Islam in somalia
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About Ahmad Gurey and the conversions to Islam
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It's not an easy question that i can answer specially since somalia doesn't have a long literally tradition of recording it's own history nor is there an extensive outside source that kept an account on the history of somalia. Overall we can only speculate based on evidence from the few mentions of somalis in foreign record.
Now for starters the somali coast had a strong connection with the arabian peninsula prior to the advent of islam and that had been noted in the periplus where it mentions boats sailing from the somali coast to the opposite coast of arabia peninsula for trade.
Somalis have been mentioned in numerus pre islamic arabian poetry which further points out the extensive relationship between somalis and the arabian coast.
ุนูู ูู ู
ูุตูุต ุงูุฐูุงุจู ู
ุนุงูุฏ ... ุจุฑูุฏ ุงูุณุฑู ุจุงูููู ู
ู ุฎูู ุจุฑุจุฑุง
ููุงูุช ุงูุฎูู ุงูุจุฑุจุฑูุฉ ุชููุจ ุฃุฐูุงุจูุง ูุงูุจุบุงูุ ูุชุฏุฎู ู
ุฏุงุฎููุง ูู ุฎุฏู
ุฉ ุงูุจุฑูุฏุ ูููุนูู
ุฃููุง ููู
ูู
ูุฎุต ุฎูู ุจุฑุจุฑ ูุฃููุง ูุงูุช ุฃุตูุจ ุงูุฎูู ุนูุฏูู
ูุฃุฌูุฏูุง
ูุจุนุฏ ุฃุจู ูู ุญุตู ููุฏุฉ ุณูุฏุง *** ูุณูุฏ ุฌู
ูุนุง ู
ู ุฌููุด ูุจุฑุจุฑุง
From this it's easy to assume some somali trader and or somalis that settled yemen or anywhere else in arabia were the first to convert around the early days of islam followed by coastal cities in somalia. We're talking about the 7th and 8th century.
What further enforces this notion is the presence of riwaq al-jabarti/zayla'i or the portico of jabarti/zayla'i You see the portico of jabarti/zaylaci is found in al azhar university which is if i remember correctly the oldest continues university in the world. It was established in 970 ad and the portico of jabarti is as old as the university itself. That being said the portico of jabarti is much older than the university and was first founded in the umayyad mosque of modern day syria, meaning that it might be as old as the 9th or 8th century for all we know.
Finally when it comes to the somali coast the oldest mention of them being muslims that i can find is the account of al-idrisi that dates back to 1155 ad which mentioned the somali coast with the exception of barawe being muslim and even mentioned some interior settlement connected to the coast. Now al-idris didn't care much for the somali coast so much so that he miss spelt zaylac and didn't even mention mogadishu so there might be some information he didn't even bother to mention. Ibn sa'd that came a century later explicitly mentioned that the whole somali coast was muslim and even mentioned some interior cities being muslim too.
The somali coast conversion to islam must be very early in history which is a necessity since the interior in places such as shewa on so on had a long islamic tradition dating back further than the 11th century but unless we have some sort of record or manuscript from say yemen or any other place we cannot be hundred percent sure of that.