Is it wajib to wear a topi?

It is not Waajib to wear a Topi. It is Sunnah.%0D%0A%0D%0AA Muslim male should wear the Topi at all times. If he unfortunately does%0D%0Anot do so, then he should at least respect the Salaat and put on a Topi for%0D%0ASalaat. Your friend's claim is incorrect. (Refer below)%0D%0A%0D%0Aand Allah Ta'ala Knows Best%0D%0A%0D%0AMoulana Imraan Vawda%0D%0AFATWA DEPT.%0D%0A%0D%0ACHECKED AND APPROVED CORRECT: Mufti Ebrahim Desai%0D%0A%0D%0AAbu Kabsha (Radhiallaahu %C1nhu) narrates that the hats of the companions of%0D%0ARasulullah (Sallallaahu Alayhi Wasallam) used to be round and spacious.%0D%0A(Mirqaat vol.8 pg.246)%0D%0A%0D%0AIt is narrated by Tabrani on the authority of Ibn Umar (Radhiallaahu %C1nhuma)%0D%0Athat Rasulullah (Sallallaahu Alayhi Wasallam) used to wear a white hat.%0D%0A(Ibid)%0D%0A%0D%0AHassan Basri (Rahmatullah Alayhi) states that the people (Sahaaba -%0D%0ARadhiallaahu Anhum) used to make Sajda (prostrate) upon their turbans and%0D%0Ahats. (Bukhari vol.1 pg.56; Rashidiyya)%0D%0A%0D%0AMullah Ali Qari (Rahmatulah Alayhi) states that the wearing of the hat has%0D%0Abecome one of the salient symbols of Islam. (Mirqaat vol.8 pg.246) It is the%0D%0Aonly outward and unique salient feature that distinguishes a Muslim from a%0D%0Anon-Muslim. No other community group or people wear the Muslim type hat%0D%0A%0D%0A