When a jew avoids an important obligation on Saturday because it is the sabbath. He or she is "Pulling a Koufax".
-Making reference to the great Jewish baseball pitcher Sandy Koufax who had to miss a world series game because it was a high holy day, and put his team in jeopardy of losing.
David: I can not play golf this saturday.
Larry: Why can't you play golf on saturday?
David: Its the sabbath, the most important day of the week for us jews.
Larry: So you are Koufaxing me?
David: I have to respect the sabbath!