Learn more about Pharisees from the Easton’s Bible Dictionary

Separatists (Heb. persahin, from parash, "to separate"). They were probably the successors of the Assideans (i.e., the "pious"), a party that originated in the time of Antiochus Epiphanes in revolt against his heathenizing policy. The first mention of them is in a description by Josephus of the three sects or schools into which the Jews were divided (B.C. 145). The other two sects were the Essenes and the Sadducees. In the time of our Lord they were the popular party (John 7:48). They were extremely accurate and minute in all matters appertaining to the law of Moses (Matt. 9:14; 23:15; Luke 11:39; 18:12). Paul, when brought before the council of Jerusalem, professed himself a Pharisee (Acts 23:6-8; 26:4, 5).
There was much that was sound in their creed, yet their system of religion was a form and nothing more. Theirs was a very lax morality (Matt. 5:20; 15:4, 8; 23:3, 14, 23, 25; John 8:7). On the first notice of them in the New Testament (Matt. 3:7), they are ranked by our Lord with the Sadducees as a "generation of vipers." They were noted for their self-righteousness and their pride (Matt. 9:11; Luke 7:39; 18:11, 12). They were frequently rebuked by our Lord (Matt. 12:39; 16:1-4).
From the very beginning of his ministry the Pharisees showed themselves bitter and persistent enemies of our Lord. They could not bear his doctrines, and they sought by every means to destroy his influence among the people.