Smiling takes nothing from you, rather it's an avenue to gain enormous reward. When you smile to someone, it serves as charity. The Holy Prophet (peace be upon him) said: "When you smile to your brother's face, it is charity."
This is an authentic hadîth. It is related in Sunan al-Tirmidhî (1879) and al-Tirmidhî declared it to be good. It is also related in Sahîh Ibn Hibbân(475 & 530) and Musnad al-Bazzâr.
There is great wisdom in the Prophet's words: "When you smile to your brother's face is charity."
And indeed, the Prophet (peace be upon him) followed this advice in his everyday life, so much so that `Abd Allah b. al-Hârith said: "I have never seen anyone more in the habit of smiling than Allah's Messenger." [Sunan al-Tirmidhî (3574)]
The prophet (peace be upon him) saw a smile as a gift of joy – an emotional gift, not a material one – a gift whose substance is received by the heart.
When the Prophet (peace be upon him) said: "your brother's face" he was not implying that smiling is only prescribed upon meeting someone. This advice applies to every occasion where a smile can bring cheer, lighten the mood, or reduce the stress that people are feeling.
Jarîr b. `Abd Allah said: "Since the time I accepted Islam, the Prophet (peace be upon him) never once failed to notice me. Whenever he saw me, he would smile at me." [Sahîh al-Bukhârî (2809 & 5625) and Sahîh Muslim (4523)]
For a smile to be a habitual part of your personality, the facial muscles must be accustomed to smiling. In this way, the hesitancy that we feel when meeting someone, the uncertainty that often comes with interpersonal dealings, will not us from being able to give a broad, heartfelt smile.
There are people who consider frequent smiling to show a deficiency in intelligence or social status. Then there are those who try to smile, but are so unaccustomed to doing so that with great effort they barely manage to curl their lips noticeably. Such people should practice smiling on their own if they must. Maybe they should think of a humorous incident to bring a smile to their face and then share that smile with someone else at no extra cost!
May Allah guide us.
