Sahih Al Bukhari – Book of To Make The Heart Tender (Ar-Riqaq)
Volumn 008, Book 076, Hadith Number 497.
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Narated By Abu Huraira RA : Allah's Apostle PBUH said, "If anyone of you looked at a person who was made superior to him in property and (in good) appearance, then he should also look at the one who is inferior to him, and to whom he has been made superior."