Capitalized:
* When referring to the specific Ten Commandments: "The Ten Commandments are a set of religious laws."
* When used as a formal title: "The Book of Commandments"
Not capitalized:
* When referring to commandments in general: "Many religions have commandments for their followers."
* When used in a casual sentence: "He followed the commandments of his parents."
In short, capitalize "Commandments" when referring to the specific Ten Commandments or when using it as a formal title, but not in general use.