Matthew 23:27 - Ellicott's Commentary On The Whole Bible

Ye are like unto whited sepulchres. — Contact with a sepulchre brought with it ceremonial uncleanness, and all burial-places were accordingly white-washed once a year, on the 15th day of the month Adar — i.e., about the beginning of March — that passers-by might be warned by them, as they were of the approach of a leper by his cry, “Unclean, unclean!” (Leviticus 13:45). The word translated “whited,” means literally, “smeared with lime powder” — i.e., “whitewashed,” in the modern technical sense of the word. It should be noticed that the similitude in Luke 11:44 is drawn from the graves that were not whitened, or from which the whitewash had been worn away, and over which men passed without knowing of their contact with corruption. Some have thought, indeed, that this passage also refers to graves which had lost the coat of whitewash, and were “beautiful with grass and flowers.” It seems hardly likely, however, that the perfect participle would be used to describe such a state of things, and it is more probable, looking to the date above given, that our Lord pointed to some tombs that were shining in their new whiteness.