As someone else mentioned it's probably the ces letter, but it also could be this one: https://www.letterformywife.com/the-letter https://www.letterformywife.co

As someone else mentioned it's probably the ces letter, but it also could be this one: https://www.letterformywife.com/the-letter https://www.letterformywife.com/the-letter http://www.mormonthink.com/lying.htm http://www.mormonthink.com/lying.htm is another good read.