“Woe to you, scribes and Pharisees, hypocrites! for you are like whited sepulchres, which outwardly appear beautiful, but inwardly are full of dead men's bones, and of all uncleanness. Even so you also outwardly appear righteous to men, but inwardly you are full of hypocrisy and lawlessness.”
It was the custom in Palestine as the Feast of Passover approached, to generally clear up the highways and especially to mark the graves. This would be done by whitewashing them, so that pilgrims who did not know the district would not accidentally come into contact with them and be rendered ‘unclean' for seven days (Numbers 19:16), thus missing out on the Feast. Thus for a time they looked sparkling white, they were ‘beautiful'. But it did not obscure the fact that inside the tombs were rotting flesh and dead men's bones. The same was true of the Scribes and Pharisees. They put on a show on the outside but they were dead and putrefying inside.
We do not need to over-emphasise ‘beautiful'. Jesus is not setting an aesthetic standard but indicating the difference between an unkempt and uncared for grave, and their smartness once they had been cleaned up and painted, and looked respectable. Indeed in many cases the whitewashing would draw attention to their beauty, for the purpose of tombstones and monuments was often in order to be ‘beautiful' as the resting place of their occupants. It is, however, quite possible that people did tend to try to actually beautify them as well, especially at such times.
Jesus applies the picture to the Scribes and Pharisees. They too ‘whitewashed' themselves by their ritual activities, but were inwardly unclean, ‘full of hypocrisy and lawlessness'. They were in total contrast with the pure in heart (Matthew 5:8) who saw God. The charge of ‘lawlessness' is especially poignant, for they prided themselves on observing the Law. But that was their problem. They selected which parts they would keep, and those tended to concentrate on the religious ritual which was observable by God and men. Instead of being pure in heart (Matthew 5:8) they were whitewashed on the outside. There may also be a reference in this ‘whiteness' to the fact that some wore white robes in order to make an impression of purity.