“The question Jesus posed to His disciples is the ultimate question for us: “Who do you say that I am?” Do you believe that Jesus is the Messiah? When we stand up publicly and join a church, we declare to our friends, our neighbors, and all the watching world: “I believe that Jesus is the Messiah. I believe He is the Christ. I believe that HE is the Son of the living God.” If you believe that, the same benediction that Jesus pronounced on Peter is your benediction. He says,”Blessed are you,” because this is not something you learned in kindergarten, from the newspaper, or from the TV news. Flesh and blood do not reveal this kind of information. If you believe in your heart that He is the Christ, you are blessed above all people because God has allowed you to see this truth. If you are ever downcast; if you are ever jealous of someone else’s status or possessions, if you ever cry to God, “Why me?” in the midst of affliction, hear these words: “Blessed are you.” You have been enabled to recognize the pearl of great price, and if God never gives you another blessing for the rest of your days on this earth, you will have no reason to do anything else but proclaim His glory and His mercy to the whole world, because the greatest blessing a human being can ever receive is the blessing of knowing him.
– from Mark, St. Andrew’s Expositional Commentary