Clothing (Kitab Al-Libas)
Dawud :: Book 32 : Hadith 4071
Narrated Qurrah ibn Iyas al-Muzani:
I came to the Apostle of Allah (peace_be_upon_him) with a company of Muzaynah and we swore allegiance to him. The buttons of his shirt were open. I swore allegiance to him and I put my hand inside the collar of his shirt and felt the seal.
Urwah said: I always saw Mu'awiyah and his son opening their buttons of the collar during winter and summer. They never closed their buttons.