Slave or son?

I really like Glen Scrivener's opening to his sermon on Gal. 4:1-3. Here it is: 

Two boys at work in a field. (Gal 4:1-3).

They look the same, but they couldn’t be more different.

One is a slave, the other is a son.  One is property, the other is heir.  One calls the owner “Boss”.  The other calls him “Daddy.”

But from a distance you can’t tell.

In church, slaves and sons sit side by side.  And, from a distance, you can’t tell which is which.  But actually there is a profound difference in their relationship to the Father – and this difference is decisive.

Yes, it is.