In The Garden: Need to ID this tree

I was cleaning out my old plant pots and came across this small tree growing in one of them. Can anyone ID what kind of tree this is by looking at the leaves? Thanks.

 

An oak seedling - likely an acorn hidden and then forgotten by a squirrel.

 

"Great oaks from little acorns grow."

I'd definitely keep it unless there is a good place to plant it wild. A treasure.

 

Thanks for the response. I will plant it in a nice place so it will grow old and strong.