Musnad Abu Ya'la al-Mawsili 117:71

Hawthara ibn Ashras narrated to us, Hammad ibn Salama narrated to us, from Thabit al-Bunani, from Anas ibn Malik, who said: The she-camel of the Messenger of Allah (peace be upon him), al-Adba', would not be outrun. Then a Bedouin came with a young camel of his and raced it, and the Bedouin outran it. This was difficult for the companions of the Messenger of Allah (peace be upon him). So he (the Prophet) said: "It is a right upon Allah that He does not raise anything in the world except that He lowers it."