Sahih Bukhari Volume 003, Book 036, Hadith Number 468.
Narated By Ibn 'Umar : The Prophet said, "Your example and the example of the people of the two Scriptures (i.e. Jews and Christians) is like the example of a man who employed some laborers and asked them, 'Who will work for me from morning till midday for one Qirat?' The Jews accepted and carried out the work. He then asked, Who will work for me from midday up to the 'Asr prayer for one Qirat?' The Christians accepted and fulfilled the work. He then said, 'Who will work for me from the 'Asr till sunset for two Qirats?' You, Muslims have accepted the offer. The Jews and the Christians got angry and said, 'Why should we work more and get lesser wages?' (Allah) said, 'Have I with-held part of your right?' They replied in the negative. He said, 'It is My Blessing, I bestow upon whomever I wish.'