Grasping another person's hand (typically the right or dominant hand). This could be a sign of greeting, farewell, welcome, or affirmation.
Key passages
Ga 2:9

and when James and Cephas and John—those thought to be pillars—acknowledged the grace given to me, they gave to me and Barnabas the right hand of fellowship, in order that we should go to the Gentiles and they to the circumcision.