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