Sunan Abu Dawud
999
Sahih+3

The aforesaid tradition has also been narrated by Mis’ar through a different chain of transmitters to the same effect. This version adds:Is it not sufficient for one of you or for one of them that he puts his hand on his thigh, and then gives the salutation to his brother to his right and left sides

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid