[Machine] Smiling does not invalidate the prayer, but laughing out loud is what is prohibited and is considered a disruption. This ruling has been stated by Thabit ibn Muhammad al-Zahid and it is a consensus among scholars.  

التَّبَسُّمُ لَا يَقْطَعُ الصَّلَاةَ وَلَكِنِ الْقَرْقَرَةُ هَذَا هُوَ الْمَحْفُوظُ مَوْقُوفٌ وَقَدْ رَفَعَهُ ثَابِتُ بْنُ مُحَمَّدٍ الزَّاهِدُ وَهُوَ وَهْمٌ مِنْهُ  

[Machine] The Prophet ﷺ said, "The prayer is not interrupted by hiccups, but it is interrupted by laughter. And it has been narrated in another hadith regarding smiling during prayer which cannot be used as evidence."  

عَنِ النَّبِيِّ ﷺ قَالَ لَا يَقْطَعُ الصَّلَاةَ الْكَشْرُ وَلَكِنْ يَقْطَعُهَا الْقَرْقَرَةُ وَقَدْ رُوِيَ فِي التَّبَسُّمِ فِي الصَّلَاةِ حَدِيثٌ آخَرُ لَا يُحْتَجُّ بِأَمْثَالِهِ  

[Machine] We used to pray with the Messenger of Allah ﷺ in a battle. He smiled during his prayer, and when he finished his prayer, we said, "O Messenger of Allah, we saw you smiling." He said, "Mikael passed by me with traces of dust on his wings, as he was returning from seeking the people's needs, and he smiled at me, so I smiled at him." Al-Wazi' ibn Nafi' al-Qa'ili al-Jazari spoke about it, and Al-Waqidi narrated it in the battles. It has also been narrated in the book of purification from Abu Sufyan from Jabir that whoever laughs in prayer should repeat the prayer but not repeat the ablution. And we have also narrated from Abu Musa al-Ash'ari that he said in a story narrated from him: whoever among you laughs, let him repeat the prayer and mention the same from Ibn Mas'ud.  

كُنَّا نُصَلِّي مَعَ رَسُولِ اللهِ ﷺ فِي غَزْوَةٍ إِذْ تَبَسَّمَ فِي صَلَاتِهِ فَلَمَّا قَضَى صَلَاتَهُ قُلْنَا يَا رَسُولَ اللهِ رَأَيْنَاكَ تَبَسَّمْتَ قَالَ مَرَّ بِي مِيكَائِيلُ وَعَلَى جَنَاحِهِ أَثَرُ غُبَارٍ وَهُوَ رَاجِعٌ مِنْ طَلَبِ الْقَوْمِ فَضَحِكَ إِلَيَّ فَتَبَسَّمْتُ إِلَيْهِ الْوَازِعُ بْنُ نَافِعٍ الْعُقَيْلِيُّ الْجَزَرِيُّ تَكَلَّمُوا فِيهِ وَقَدْ حَكَاهُ الْوَاقِدِيُّ فِي الْمَغَازِي وَقَدْ رُوِّينَا فِي كِتَابِ الطَّهَارَةِ عَنْ أَبِي سُفْيَانَ عَنْ جَابِرٍ فِي مَنْ ضَحِكَ فِي الصَّلَاةِ يُعِيدُ الصَّلَاةَ وَلَا يُعِيدُ الْوُضُوءَ وَرُوِّينَا عَنْ أَبِي مُوسَى الْأَشْعَرِيِّ أَنَّهُ قَالَ فِي قِصَّةٍ مَحْكِيَّةٍ عَنْهُ مَنْ كَانَ ضَحِكَ مِنْكُمْ فَلْيُعِدِ الصَّلَاةَ وَيُذْكَرُ مِثْلُ ذَلِكَ عَنِ ابْنِ مَسْعُودٍ