Why did Jesus call the religious leaders whited sepulchers?
Jesus called them whited sepulchers because their religion was dead and had no spiritual life whatsoever. Though they maintained outward religious practice, they were not true believers in the God of Abraham; only a small remnant remained faithful, while the rest were cloaked in nothing more than empty religion.
Les explains that when you come to Christ's first advent, most people assume the Jews were largely an obedient people, but they were not. Only a few were left as true believers, such as Zacharias and Elizabeth, Joseph and Mary. The rest had been cloaked in nothing more than their religion—a dead religion. That is why Jesus called them whited sepulchers, because they were a dead religion with no spiritual life whatsoever.