Sayyiduna Jabir bin Samurah (may Allah be pleased with him) narrates: When we prayed behind the Messenger of Allah (peace and blessings be upon him), we would say, pointing with the index finger: 'As-salamu 'alaykum, as-salamu 'alaykum' (Peace be upon you, peace be upon you). The Prophet (peace and blessings be upon him) said: "What is the matter with people that they raise their hands in the prayer as though they were the tails of restive horses? Is it not enough for you, or he said: for them, that one places his hand on his thigh and then gives salam to his brother on his right and on his left?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2960