The Prophet Mohammed and the Olive Tree
Contributed by Arab Educational Institute on 17.03.2006:
When the Prophet Mohammed died all the trees mourned and cast down their leaves. Then came one and said to the Olive Tree, ‘O Olive Tree, the Prophet is dead and all the trees mourn and why do you not mourn?’ The Olive Tree replied, ‘Break my wood and see the grief within at my heart.’ So he broke a branch from the Olive Tree and saw the grief in her heart. For her grief was within and not to be seen by men.”
So to this day you can see the black streak in the wood of the Olive, which is the sign of her mourning.
Source: Grace Crawfoot and Louise Baldensperger, From Cedar to Hyssop: A Study in Plant Folk Lore.