Pharisees were a Jewish sect (or religious-political party) which arose during the intertestamental period and were active during Christ's earthly ministry described in the gospels of the New Testament. They were noted for strict observance of rites and ceremonies of the written law and for insistence on the validity of their own oral traditions concerning the law. The Pharisees opposed Jesus and His teachings. They plotted His death (Matt 12:14) and they were denounced by Him (Matt 23).
Pharisees were distinguished from the Sadducees (the priestly caste) primarily as scribes and devout laymen. The pharisees developed the synagogue as a place of worship beyond the temple. Characteristic teachings of the pharisees included: belief in oral as well as written Law; resurrection of the human body; belief in the existence of a spirit world; immortality of the soul; predestination; future rewards and punishments based upon works.
Pharisaism had its beginnings in the Maccabean times (approx. 165 BC) when the threat of persecution was driving many Jews to relinquish their distinctive manner of life and accept Greek ways. The First Book of Maccabees tells the story. They were called upon to eat pork, and renounce the food laws of Leviticus, to give up their copies of the Law to their persecutors, and let the Temple be profaned and their children to go uncircumcised. But some stoutly refused to accede to these demands, preferring at whatever peril to separate themselves from the rest and declare their complete devotion to the service of God. (The very word Pharisee is a derivative from a Hebrew word meaning separatist) They professed to be God's people with no other purpose in life than to carry out His will as revealed in the Law. So arose the Pharisees, as the Puritans of Judaism.
This would be the nobler side of Pharisaism; however, its weakness lay in its tendency to direct the Pharisee's attention, not to spiritual fellowship with God, but to the written Law as the final expression of His will, so that religion became not a great inward experience but the meticulous performance of a technique. Further, since it assumed that the Law was the full expression of the will of God, it envisaged the possibility that a man might carry it out so completely that God Himself could ask no more of him. It resulted in spiritual pride and caused the Pharisees to degenerate into a sort of religious aristocracy.
Ultimately, Pharasiasm became quite harsh; a religiosity that truly hated its enemies. It is the kind Jesus encountered in Galilee and condemned in His Sermon on the Mount. It was the kind that took no second thought to the stoning of Stephen, Christanity's first martyr. It certainly left a great disappointment in the soul of Saul of Tarsus, who, after devoting an entire lifetime to the call of the Pharisee, still found no fulfillment in the minutiae of detail of ceremonial cleanness. In the book of Romans, many small passages reveal the apostle's joy in being released from his former spiritual bondage when he ultimately placed all his trust in Christ. (Paul, A Biography, Edgar J. Goodspeed, pg. 11-12, 1947, Abington Press)