Volume 3, Book 43, Number 635:
“We were in Medina with some of the Iraqi people, and we were struck with famine and Ibn Az-Zubair used to give us dates. Ibn ‘Umar (radiallaahu `anhu) used to pass by and say, “The Prophet (sallallaahu `alayhi wasallam) forbade us to eat two dates at a time, unless one takes the permission of one’s companions.”
When we’re sharing food with someone, you can’t have more than what they’re having. If they take a bite, you take an equal bite. If you want a bigger one, seek permission. And that’s how you share food!