It has been reported from Ummi Salamah Radhiyallahu 'Anha:
"Rasulullah Sallallahu 'Alayhi Wasallam preferred wearing, from among all clothing, the qamis (thowb)" (DE)
English reference (DE): Book 8, Hadith 55 (DE)
Arabic reference (DE): Book 8, Hadith 56 (DE)