Reminding people of an embarrassing incident or of their chequered past, or even putting them in an awkward position by volunteering them for a favour or job that they do not want to or cannot do are examples of ona’at devarim, verbal oppression. It is rooted in the verse, “Do not oppress one another, but fear your God” (Leviticus 25:17). Rashi explains that this refers to ona’at devarim.
Discussing one’s fabulous holiday in the presence of people who might be pained or envious by your story is likewise included.
The verse prohibiting ona’at devarim concludes with the words “but fear your God”. This phrase tells us that while we may be able to play dumb and pretend that we had no idea that our words were causing anyone pain, “the Knower of thoughts knows”. As Rashi says in several places “anything entrusted to our conscience that does not exact a [social] price bears the words ‘But fear your God’.” It’s up to us to be honest about our own true intentions.