I couldn't find the exact source of this quote, so this may be more paraphrase than quote. There's also this article from 2019:
https://www.heraldscotland.com/news/17949861.billy-connolly-scottish-story/
QuoteThe Scots and the Irish – Connolly is of Irish stock as his surname tells you – have a deep cultural quirk of respecting death, but never taking it too seriously. Connolly will be keeping up that tradition. He’s told his wife Pamela Stephenson that when he dies he wants an epitaph in tiny writing so visitors will have to step close to his gravestone to read it. When they can finally see it, they’ll discover it says: “You’re standing on my b***s”.