He traced it back to the Prophet ﷺ, who said, "None of you should look at those above him in appearance, character, or wealth, but rather look at those below him."
حدثنا سفيان عن أبي الزناد عن الأعرج
يبلغ به النبي ﷺ لا ينظر أحدكم إلى من فوقه في الخلق أو الخلق أو المال ولكن ينظر إلى من هو دونه
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Its isnad is sahih. Something similar in meaning will come from two other routes, 7442 and 8132. Bukhari also narrated something similar to it, 11:276, through the route of Malik from Abu Zinad. Muslim also narrated something similar to it, 2:384-385, through the route of Mughira bin Abdul-Rahman, from Abu Zinad. Then after it, from two other routes.