From the Shorter Catechism
Q. 61. What is forbidden in the fourth commandment?
A. The fourth commandment forbiddeth the omission, or careless performance, of the duties required, and the profaning the day by idleness, or doing that which is in itself sinful, or by unnecessary thoughts, words, or works, about our worldly employments or recreations. Ezek. 22:26; Amos 8:5; Mal. 1:13; Acts 20:7, 9; Ezek. 23:38; Jer. 17:24-26; Isa. 58:13.