Jesus’ image of the Pharisees as “white-washed graves” is multi-dimensional.

First, there is the obvious contrast between the apparently pure outside (white) and the inside (bones and uncleanness). In context, the Pharisees have become filled with corpses by devouring other Jews. They are cannibals, insatiable as the grave.

Second, as Duncan Derrett points out, tombs were white-washed at Passover to enable pilgrims to avoid contamination caused by inadvertently stepping on a grave. When they make themselves all “white” on the outside, of course, the Pharisees and scribes are not thinking of themselves as tombs that need to be marked, but that’s what they are.

This implies, third, that their hypocritical scrupulosity about outward purity marks them as impure. Jesus says, in effect: “Do you want to know how to identify tomb-teachers, cannibal-shepherds? Look for the ones who have marked themselves as tombs. Look for the ones who are really pure.”

And, fourth, “avoid them.” If the Pharisees and scribes are tombs, they are also defiling. Everyone who follows the Pharisees will be contaminated by them. They spread death.

There may, finally, be another level to this. Duncan Derrett translates oraios not as “beautiful” but as “timely, seasonable.” The Pharisees make themselves seasonably white; they are especially concerned with purity in the time Jesus speaks to them because Passover is coming. But the extra shine they put on themselves for Passover is like the white-wash put on graves: “Pharisees putting the final touch to whitewash on graves (i.e. themselves) made themselves entirely ‘seasonable’: the incongruity did not strike them.”