A pack of playing cards is in the devil's prayer book.

Understand the thought

Meaning in plain English

Playing cards placed in the devil’s prayer book gives a pastime a severe moral or religious condemnation. The saying associates cards with an imagined harmful influence.

What the words are saying

This is a moral outlook, not a verified supernatural fact or proof that every card game is gambling or harmful. A critical reading can examine particular stakes, pressure and consequences without condemning all players. No precise doctrine or original tradition is asserted here.

Everyday example

Someone considers the actual conditions of a game rather than judging every player through a supernatural label.

When to use it

Use it critically as one moral view of a pastime.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.