What is the pejorative for people who only practice their faith while at the place of worship?

Among Catholics, there is the pejorative Cafeteria Catholic for those who selectively pick and choose which tenets of the faith they obey in their daily lives. Someone who attends Mass and says the catechisms on Sunday, yet still supports abortion rights and eats meat on Lent, is considered a hypocrite in the sense you offer by some other Catholics.

EDIT: Sunday Christian seems to be pretty official; as proof, there's even a Wikipedia article on the subject. The article offers other synonyms such as Sunday-morning Christian, Once-a-weeker, Chreasters (coined of Christmas and Easter [Christians]), Twice-a-years and Submarine Christians (so-called because they only surface a few times every year.)

Whited sepulchres. This is what they are called in the Bible, King James' Version.