Gospel of Mark, Chapter 8, verses 11-13
On this Feast of Ss. Cyril & Methodius (ok, and St Valentine!), Jesus is confronted (I'm shocked!) by the Pharisees, demanding a sign from heaven to test Him.  This is immediately following Jesus's feeding of the 5,000 - so I'm not quite sure how they missed that one.  Their eyes are closed to what is all around them.  And while it's easy to chuckle from a distance, are we all that different?  
Ss. Cyril, Methodius and Valentine, pray for us.