Matthew 23:27

like unto whited sepulchres In Luke the comparison is to "graves that appear not," by walking over which men unconsciously defile themselves. To avoid this ceremonial defilement the Jews carefully whitewashed the graves or marked them with chalk on a fixed day every year the fifteenth of Adar. The custom still exists in the East. One of the spiteful devices of the Samaritans against the Jews was to remove the whitewash from sepulchres in order that the Jews might be contaminated by walking over them.