Sahih al-Bukhari 6490
Narrated Abu Huraira:
Allah's Messenger (ﷺ) 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.
حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ ‏
"‏ إِذَا نَظَرَ أَحَدُكُمْ إِلَى مَنْ فُضِّلَ عَلَيْهِ فِي الْمَالِ وَالْخَلْقِ، فَلْيَنْظُرْ إِلَى مَنْ هُوَ أَسْفَلَ مِنْهُ ‏"‏‏.‏