This Mishnaic passage indicates that the Pharisees observed purity laws at a level which placed them between the common people and the priestly families who ate of the terumah offerings.
The clothing of an ‘am ha-’arez 91 is the source of the highest level of defilement for the Pharisees. The clothing of Pharisees is the source of the highest level of defilement for those who eat the priestly portion. The clothing of those who eat the priestly portion is the source of the highest level of defilement to those who eat sacrifices. The clothing of
those who eat sacrifices is a source of the highest level of defilement to [those priests who sprinkle the water of] the sin-offering. 92
90. Trans. S. Berrin.
91. One of the common people who were not strict in the observance of the laws, ritual purity or the tithing of produce.
92. Cf. Num. 19-9. This refers to the preparation of the water of purification from impurity of the dead after the sacrifice of a red heifer.