The earliest credible evidence of coffee-drinking or knowledge of the coffee tree appears in the middle of the 15th century in the accounts of Ahmed al-Ghaffar in Yemen. It was here in Arabia that coffee seeds were first roasted and brewed in a similar way to how it is prepared now. Coffee was used by Sufi circles to stay awake for their religious rituals. Accounts differ on the origin of the coffee plant prior to its appearance in Yemen. From Ethiopia, coffee could have been introduced to Yemen via trade across the Red Sea. One account credits Muhammad Ibn Sa'd for bringing the beverage to Aden from the African coast. Other early accounts say Ali ben Omar of the Shadhili Sufi order was the first to introduce coffee to Arabia. According to al Shardi, Ali ben Omar may have encountered coffee during his stay with the Adal king Sadadin's companions in 1401.