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If a person begins by telling you, 'Do not be offended at what I am going to say,' prepare yourself for something that she knows will certainly offend you.

Eliza Leslie (1839). “Miss Leslie's Behaviour Book: A Guide and Manual for Ladies as Regards Their Conversation; Manners; Dress; with Full Instructions and Advice in Letter Writing [!]; Receiving Presents; Incorrect Words”, p.208
If a person begins by telling you, 'Do not be offended at what I am going to say,' prepare yourself for something that she knows will certainly offend you.