Call Me Gilgamesh

I remember in 9th grade when we were studying mythology, that my teacher told us about a religion that believed that the sole requirement for passage into heaven after death, was that the individual had to have had at least one friend in life. I found this both sad and beautiful. What if the person was an outcast who had problems making friends, but was really good at heart? That was the sad thought. The idea though, that the most important thing in all the world was to connect with at least one other human being, that's what I found beautiful.

I forget which culture it was that held this belief. For a long time, I had thought it was the ancient Sumerians, but it seems that they had a universally dim view of the afterlife for all, so it couldn't have been them. I've poked around a bit, and I'm unable to find it. I'm starting to think maybe my teacher was confused, on making it up, or both. Either way, I'm sticking with it.