Isaiah and Luke are more connected that we may initially think today. Isaiah is talking about including outsiders in worship, and then turns to his own to point out how unfit they are as a holy people. Luke gives us the well-known parable of the prodigal son... and the other son. It is in the son who stayed home, who never broke the rules, where we may find a hard lesson for ourselves. Do you see the major difference in the relationship the two have with the father? The younger son goes out rambling, but his thought is to return to his father. The other son, the one who symbolizes the chosen people of God, gets mad because there was not party for him. But what does he say? "You never gave me even a young goat so I could celebrate with my friends." In the party he wishes he had, he celebrates with his friends and not his father. We must be careful not to do the same. It's easy to get so focused on our own tribe that we forget that our most important connection is with out heavenly Father.