"The Messenger of Allah ﷺ came out to us and we were raising our hands during the Salah. He said: 'Why are you raising your hands while praying, like the tails of wild horses? Stay still when you are praying.'" (Using translation from Nasāʾī 1184)  

خَرَجَ عَلَيْنَا رَسُولُ اللهِ ﷺ وَنَحْنُ يَعْنِي رَافِعُو أَيْدِينَا فِي الصَّلَاةِ فَقَالَ «مَا بَالُهُمْ رَافِعِينَ أَيْدِيَهُمْ فِي الصَّلَاةِ كَأَنَّهَا أَذْنَابُ الْخَيْلِ الشُّمْسِ اسْكُنُوا فِي الصَّلَاةِ»  

"We used to pray behind the Messenger of Allah ﷺ and we would greet (others) with our hands. He said: 'What is the matter with those who greet (others) with their hands as if they were tails of wild horses? It is sufficient for any one of you to put his hand on his thigh and say: "As-salamu 'alaikum, as-salamu 'alaikum." (Using translation from Nasāʾī 1185)  

كُنَّا نُصَلِّي خَلْفَ النَّبِيَّ ﷺ فَنُسَلِّمُ بِأَيْدِينَا فَقَالَ مَا بَالُ هَؤُلَاءِ يُسَلِّمُونَ بِأَيْدِيهِمْ كَأَنَّهَا أَذْنَابُ خَيْلٍ شُمْسٍ أَمَّا يَكْفِي أَحَدُهُمْ أَنْ يَضَعَ يَدِهِ عَلَى فَخِذِهِ ثُمَّ يَقُولُ السَّلَامُ عَلَيْكُمْ السَّلَامُ عَلَيْكُمْ