The companions of the Messenger of Allah ﷺ were one day discussing worldly matters in his presence, so the Messenger of Allah ﷺ said, "Do you not hear? Do you not hear? Simplicity in dress is part of faith. Simplicity in dress is part of faith," meaning shabbiness of appearance.
ذكر أصحاب رسول الله ﷺ يوما عنده الدنيا، فقال رسول الله ﷺ: ألا تسمعون، ألا تسمعون، إن البذاذة من الإيمان، إن البذاذة من الإيمان يعني التقحل.
Abu Dawud narrated it (4161) from Ibn Nufayl, who said, Muhammad bin Salama told us, from Muhammad bin Ishaq, from Abdullah bin Abu Umama, from Abdullah bin Kaab bin Malik, from Abu Umama, and he related it. Its chain of transmission is hasan because of Abdullah bin Abu Umama, for his hadith is hasan, but the chain contains Muhammad bin Ishaq, who practiced tadlis and narrated with an ambiguous form of transmission, though he has been corroborated.Ahmad narrated it in the Musnad (24009/58), and in Zuhd (29), as did Hakim (1/9) and Bayhaqi in Shuab (5762), all of them through the hadith of Abdul-Rahman bin Mahdi, from Zuhayr bin Muhammad Anbari Makki, from Salih bin Kaysan, that Abdullah bin Abu Umama informed him that Abu Umama informed him, and he related the hadith. The fact that Abdullah bin Abu Umama heard from his father has been established as sahih, so both routes are preserved.Abdullah said, I asked my father, I said, "What is badhadha?" He said, "Modesty in dress."Khattabi said, "Badhadha means shabbiness of appearance, and being lax about one's clothing and the like. A man is described as badh al-hayah or badi al-hayah when his appearance and clothing are worn and simple."As for taqahhul, it means striving for qahul, and qahul refers to dryness and aridness. It is said, "arid qahila," meaning barren land with no vegetation in it. The meaning is that a person should not make his clothing and outward appearance his entire concern.However, this does not conflict with cleanliness and good appearance in dress and adornment, and each of men and women has what is particular to them. Rather, what is meant is avoiding extravagance in clothing, and a prohibition against arrogance, excessive pride, and the like.