In the name of Allah
Revive a Sunnah: Passing Drinks to the Right
Narrated Anas ibn Malik:
Allah's Messenger (sallaAllahu ‘alayhi wasallam) came to our house and he asked for a drink. We milked a goat for him and then mixed it (the milk) with the water of this well of mine. I gave it to Allah's Messenger (sallaAllahu ‘alayhi wasallam) and he drank it, while Abu Bakr was on his left and 'Umar was in front of him, and a desert Arab was on his right. When Allah's Messenger (sallaAllahu ‘alayhi wasallam) had finished the drink, Umar said: Allah's Messenger, here is Abu Bakr, give him to drink; but Allah's Messenger (sallaAllahu ‘alayhi wasallam) gave it to the desert Arab and he left out Abu Bakr and Umar. And Allah's Messenger (sallaAllahu ‘alayhi wasallam) said: Those on the right, those on the right, those on the right (deserve preference). Anas (radi Allahu anhu) said: This is the Sunnah, this is the Sunnah, this is the Sunnah. [Muslim]
Just as we use our right hands for eating and drinking, we should start with our right sides when putting on clothing, stepping into the masjid, combing our hair, etc.
Also, it is Sunnah to pass something to the right and even when greeting a group, it is encouraged for us to shake hands and continue going to the right until you have greeted everyone.