If you had lived in Palestine two thousand years ago and someone called you a “whitewashed tomb” you would have been extremely insulted. Tombs were usually carved into a rocky hillside and protected by a heavy stone. Sometimes these tombs were hidden in the landscape, which could be inconvenient because Jewish tradition believed that any contact with a tomb—especially the bones or bodies inside a tomb—would render someone “unclean.” And the purification process after such contact could take up to seven days.
So to help prevent accidental contact with a tomb, every year graves were whitewashed, or marked with lime powder, which would give them a whitish glow. And so the tombs would become more conspicuous, keeping people from accidently rendering themselves unclean.
Our Lord is being extremely graphic in his words with the scribes and Pharisees—both graphic and pointed. Such an insult must have had a shocking effect on his audience. Even today, the term “whitewash” is used to indicate when someone is deliberately covering up his or her mistakes.
Our Lord doesn’t want us to be whitewashed tombs either. He doesn’t want us to project a fake glowing façade that hides any interior mess. He doesn’t want us to try to cover up our mistakes and pretend we are someone we’re not. Rather, he wants us to be real: inside and out. He wants us to find the courage to open up the unclean parts of our lives and ask for his help.