Language:
كتاب الرقاق
81  
To make the Heart Tender (Ar-Riqaq)
(30)
Chapter: To look at the one who is inferior to and not the superior
(30)
باب لِيَنْظُرْ إِلَى مَنْ هُوَ أَسْفَلَ مِنْهُ وَلاَ يَنْظُرْ إِلَى مَنْ هُوَ فَوْقَهُ
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 ‏"‏‏.‏
Reference : Sahih al-Bukhari 6490
In-book reference : Book 81, Hadith 79
USC-MSA web (English) reference : Vol. 8, Book 76, Hadith 497
  (deprecated numbering scheme)