GEN1600 The Mishnah Ethics of the Fathers 1:15 states: “Welcome every person with a pleasing countenance.”  What is the essence of this message? It teaches that if one presents even the most precious gift to someone while maintaining an unpleasant facial expression, it is considered as if he gave nothing.   Conversely, if one merely welcomes another person with a pleasing countenance, it is considered as if he gave him the most precious gift in the world, even if he did not give him anything” (Avos deRabbi Nasan 13:12).   Rambam [Maimonides] comments that one who welcomes another person in a joyful manner fulfills the Mishnah’s rule to an even greater extent, since this type of reception will make him feel truly at ease.  … People receive numerous signals, both explicit and implicit, that gauge the degree of affection with which other regard them.   The most revealing of these signals is facial expressions.   One who is not consciously aware of his facial expressions may be guilty of transmitting wrong signals; if his affection for another person is not sufficiently reflected by his facial expression, he is liable to lose that relationship.   The other person will consciously or subconsciously pick up unfriendly signals, which will in turn cause him to withdraw from the relationship.   The idea tool for expressing affection is the face.  One who masters the art of pleasant facial expressions will benefit himself and others, while one who continues to allow his facial expression to involuntarily betray his emotions will cause untold damage to himself and his acquaintances.   WAGS 26-7