Sahih Bukhari Volume 008, Book 076, Hadith Number 433.
Narated By 'Amr bin 'Auf : (An ally of the tribe of Bani 'Amir bin Lu'ai and one of those who had witnessed the battle of Badr with Allah's Apostle) Allah's Apostle sent Abu 'Ubaida bin AlJarrah to Bahrain to collect the Jizya tax. Allah's Apostle had concluded a peace treaty with the people of Bahrain and appointed Al 'Ala bin Al-Hadrami as their chief; Abu Ubaida arrived from Bahrain with the money. The Ansar heard of Abu 'Ubaida's arrival which coincided with the Fajr (morning) prayer led by Allah's Apostle. When the Prophet finished the prayer, they came to him. Allah's Apostle smiled when he saw them and said, "I think you have heard of the arrival of Abu 'Ubaida and that he has brought something." They replied, "Yes, O Allah's Apostle! " He said, "Have the good news, and hope for what will please you. By Allah, I am not afraid that you will become poor, but I am afraid that worldly wealth will be given to you in abundance as it was given to those (nations) before you, and you will start competing each other for it as the previous nations competed for it, and then it will divert you (from good) as it diverted them.'"