"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 خَيْلِ شَمْسٍ إِنَّمَا يَكْفِي أَحَدَكُمْ أَنْ يَضَعَ يَدَهُ عَلَى فَخِذِهِ ثُمَّ يَقُولُ السَّلَامُ عَلَيْكُمُ السَّلَامُ عَلَيْكُمْ