Qamees is a piece of clothing with two sleeves, generally made of sewn cotton and worn under the rest of the clothes. In the lifetime of the Prophet (PBUH) the Arabs would commonly use two simple sheets of cloth as dress, one covering the lower part of body and one wrapping its upper part. Qamees was also in vogue but very few people used it. No doubt it covers the body adequately and is also comparatively convenient. So, the Prophet (PBUH) liked it most.