The phrase "went to one's reward" is a euphemism for death. There are several synonyms that can be used to express the same idea. "Passed away" is a commonly used term that implies a peaceful death. "Expired" is another synonym that suggests the end of life. "Departed" is also a suitable word that refers to someone leaving this world. "Crossed over" is another popular phrase that implies transitioning into the afterlife. Some people simply use the term "died" to describe the end of life. Regardless of the synonym you choose, it's important to consider the sensitivity of those who may be grieving.