Sunan an-Nasai Book 13, Hadith 1185

أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا يَحْيَى بْنُ آدَمَ، عَنْ مِسْعَرٍ، عَنْ عُبَيْدِ اللَّهِ ابْنِ الْقِبْطِيَّةِ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ كُنَّا نُصَلِّي خَلْفَ النَّبِيِّ صلى الله عليه وسلم فَنُسَلِّمُ بِأَيْدِينَا فَقَالَ ‏ "‏ مَا بَالُ هَؤُلاَءِ يُسَلِّمُونَ بِأَيْدِيهِمْ كَأَنَّهَا أَذْنَابُ خَيْلٍ شُمْسٍ أَمَا يَكْفِي أَحَدَهُمْ أَنْ يَضَعَ يَدَهُ عَلَى فَخِذِهِ ثُمَّ يَقُولَ السَّلاَمُ عَلَيْكُمُ السَّلاَمُ عَلَيْكُمْ ‏"‏ ‏.‏

It was narrated that Jabir bin Samurah said:"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