"The Pharisees were a Palestinian holiness movement of laymen whose aim was the ritual sanctification of everyday life in the Eretz Israel, such as was required of priests in the sanctuary."
-- Martin Hengel, "The preChristian Paul", in Lieu, J., et alia, THE JEWS AMONG PAGANS AND CHRISTIANS IN THE ROMAN EMPIRE (Routledge, 2013), p. 37.
'"Perisha" (the singular of "Perishaya") denotes "one who separates himself," or keeps away from persons or things impure, in order to attain the degree of holiness and righteousness required in those who would commune with God (comp., for "Perishut" and "Perisha," Tan., Wayeẓe, ed. Buber, p. 21; Abot iii. 13; Soṭah ix. 15; Midr. Teh. xv. 1; Num. R. x. 23; Targ. Gen. xlix. 26).
'The Pharisees formed a league or brotherhood of their own ("ḥaburah"), admitting only those who, in the presence of three members, pledged themselves to the strict observance of Levitical purity, to the avoidance of closer association with the 'Am ha-Areẓ (the ignorant and careless boor), to the scrupulous payment of tithes and other imposts due to the priest, the Levite, and the poor, and to a conscientious regard for vows and for other people's property (Dem. ii. 3; Tosef., Dem. ii. 1). ...
'A true Pharisee observed the same degree of purity in his daily meals as did the priest in the Temple (Tosef., Dem. ii. 2; so did Abraham, according to B. M. 87a), wherefore it was necessary that he should avoid contact with the 'am ha-areẓ (Ḥag. ii. 7).'
-- Jewish Encyclopedia, "Pharisees", 1906.
And it came to pass, as Jesus sat at meat in the house, behold, many publicans and sinners came and sat down with him and his disciples. And when the Pharisees saw it, they said unto his disciples, Why eateth your Master with publicans and sinners? But when Jesus heard that, he said unto them, They that be whole need not a physician, but they that are sick. But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance.
-- Matthew 9:10ff.
