For people who are happy, pleasure, having good situation, Smiling is easy to do. Even they can laugh.
For people who have many troubles, showing smile and nice expression is hard to do. May be they can smile. But their expression show insincerity, like hide something behind it. I also difficult to smile when bad situation come.
Islam teach us to control our expression be well. Rasul PUBH was a person who have the biggest problem.
The problem which is from the families until statehood, worldly problem and everything in it until afterlife, personal problem until entire who follow him, daily habbits, manner, until problem in the heart and the mind.
But Rasulullah PBUH, was a person who always make the nicest facial expression. Sayyidina Jabir Radhiallahu ‘anhu said,
مَا رَآنِي رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ مُنْذُ أَسلَمْتُ إِلَّا تَبَّسَم فِي وَجْهِي“since I’ve converted to islam, Rasulullah PBUH never see me except he smile”
(From Shahih Bukhari no. 250)
Apparently, Smiling can change to better mood and more relax. Let’s practise with people around you. When get complicated and brewing situation, then you keep smile. You enlighten the mood.
The prophet Muhammad PBUH said,
لَا تَحْقِرَنَّ مِنَ الْمَعْرُوفِ شَيْئًا، وَلَوْ أَنْ تَلْقَى أَخَاكَ بِوَجْهٍ طَلْقٍDon’t you underestimate a little bit kindness. Despite just meet your brother with nice facial expression.
(Hadist from Muslim no. 2626)
What’s happen after that? Automatically we get it back from them. And it can fix their mood. So, Rasul PBUP said again
تَبَسُّمُكَ فِي وَجْهِ أَخِيكَ لَكَ صَدَقَةٌYour smile in front of your brother, be Handout for you.
(Sahih from Tirmidzi no 1956)
Smiling is Sunnah. It means recomendation activity from Rasulullah. If we practise it, we get reward and nearer to Rasulullah at afterlife. And thereby we get syafaa (help) from him.