Sahih Bukhari Volume 003, Book 036, Hadith Number 469.
Narated By 'Abdullah bin 'Umar bin Al-Khattab : Allah's Apostle said, "Your example and the example of Jews and Christians is like the example of a man who employed some laborers to whom he said, 'Who will work for me up to midday for one Qirat each?' The Jews carried out the work for one Qirat each; and then the Christians carried out the work up to the 'Asr prayer for one Qirat each; and now you Muslims are working from the 'Asr prayer up to sunset for two Qirats each. The Jews and Christians got angry and said, 'We work more and are paid less.' The employer (Allah) asked them, 'Have I usurped some of your right?' They replied in the negative. He said, 'That is My Blessing, I bestow upon whomever I wish.' "