All that we know of Nicodemus in the Bible is from the Gospel of John. In John 3:1, he is described as a Pharisee. The Pharisees were a group of Jews who were fastidious in keeping the letter of the Law and often opposed Jesus throughout His ministry. Jesus often strongly denounced them for their legalism (see Matthew 23). Saul of Tarsus (who became the apostle Paul) was also a Pharisee (Philippians 3:5).