Please also give me explanations of the various plcaes where covering of head is Sunnah, if it is so.
Assalaamu Alaykum Wa Rahmatullaahi Wa Barakaatuhu
Abu Kabsha (Radhiallaahu Ánhu) narrates that the hats of the companions of Rasulullah (Sallallaahu Alayhi Wasallam) used to be round and spacious. (Mirqaat vol.8 pg.246)
It is narrated by Tabrani on the authority of Ibn Umar (Radhiallaahu Ánhuma) that Rasulullah (Sallallaahu Alayhi Wasallam) used to wear a white hat. (Ibid)
Hassan Basri (Rahmatullah Alayhi) states that the people (Sahaaba – Radhiallaahu Anhum) used to make Sajda (prostrate) upon their turbans and hats. (Bukhari vol.1 pg.56; Rashidiyya)
Mullah Ali Qari (Rahmatulah Alayhi) states that the wearing of the hat has become one of the salient symbols of Islam. (Mirqaat vol.8 pg.246) It is the only outward and unique salient feature that distinguishes a Muslim from a non-Muslim. No other community group or people wear the Muslim type hat.
and Allah Ta’ala Knows Best