Bible factoid: Reading the Gospel of Luke earlier and came across Jesus calling the Pharisees “unmarked graves” in 11:44, “”Woe to you, because you are like unmarked graves, which people walk over without knowing it.” (NIV2011).
Which reminded me of when the Lord called them “whitewashed” or marked tombs in Matthew 23:37, “”Woe to you, teachers of the law and Pharisees, you hypocrites! You are like whitewashed tombs, which look beautiful on the outside but on the inside are full of the bones of the dead and everything unclean.” (NIV2011)
It strikes me that the cut of the insult is even deeper in Luke than in Matthew given the cultural context.
The Torah had prescribed that contact with a dead body would render one ritually unclean for a day. The symbolism behind this was that Yahweh is Life and contact with a corpse made the Jewish believer less of an imager of God. The Jews were so strict about this that even one’s shadow (as it is an extension of oneself) touching the tomb would render one ceremonially unclean.
So the custom was that every spring tombs would be whitewashed so people could see them clearly from a distance and thus avoid inadvertently coming upon them and becoming unclean.
In the Matthean passage it seems Jesus is saying the hypocrisy of the Pharisees is obvious (they are whitewashed) while in the Lukan passage the Pharisees and their followers are unaware of their spiritual uncleanness (they are unmarked graves) and that they spread their contamination when they come into contact with one another.