Hadith
أَخْبَرَنَا عَمْرُو بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا أَبُو نُعَيْمٍ، عَنْ مِسْعَرٍ، عَنْ عُبَيْدِ اللَّهِ ابْنِ الْقِبْطِيَّةِ، قَالَ سَمِعْتُ جَابِرَ بْنَ سَمُرَةَ، يَقُولُ كُنَّا إِذَا صَلَّيْنَا خَلْفَ النَّبِيِّ صلى الله عليه وسلم قُلْنَا السَّلاَمُ عَلَيْكُمُ السَّلاَمُ عَلَيْكُمْ . وَأَشَارَ مِسْعَرٌ بِيَدِهِ عَنْ يَمِينِهِ وَعَنْ شِمَالِهِ فَقَالَ " مَا بَالُ هَؤُلاَءِ الَّذِينَ يَرْمُونَ بِأَيْدِيهِمْ كَأَنَّهَا أَذْنَابُ الْخَيْلِ الشُّمُسِ أَمَا يَكْفِي أَنْ يَضَعَ يَدَهُ عَلَى فَخِذِهِ ثُمَّ يُسَلِّمُ عَلَى أَخِيهِ عَنْ يَمِينِهِ وَعَنْ شِمَالِهِ " .
It was narrated that Ubaidullah bin Al-Qibtiyyah said:"I heard Jabir bin Samurah say: 'When we prayed behind the Prophet (ﷺ) we used to say: As-salamu 'alaykum, as-salamu 'alaykum (peace be upon you, peace be upon you)" - and Mis'ar (one of the narrators) pointed with his hand to the right and the left. He (ﷺ) said: 'What is the matter with these people who wave their hands as if they are the tails of wild horses? It is sufficient for one to place his hands on his thighs and to say the salam to his brother to his right and left
Sahih · Abu Ghuddah
Sunan an-Nasa'i 1318 ·Book 13, Hadith 140·Also available on sunnah.com·