Musnad Ahmad 32:70

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: The she-camel of the Messenger of Allah, may Allah bless him and grant him peace, was called Al-‘Adba’, and she would not be outrun. Then a Bedouin came on a young camel and outran her. This distressed the Muslims, and when he saw what was on their faces, they said: "O Messenger of Allah, Al-‘Adba’ has been outrun." He said: "It is a right upon Allah that He does not raise anything of this world except that He lowers it."