Here's a mnemonic rhyme by E. Cobham Brewer recalling the different days set apart for rest among various religions:
CHRISTIANS worship God on Sunday;
The Sabbath day (or rest day, from Hebrew "Shabath", to rest) is the Biblical seventh day of the week (being the day when God rested after the Creation). Many Christians therefore equate the Sabbath with Sunday, but it is in fact the origin of the English word "Saturday".
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