He said: Ask the Messenger of Allah (ﷺ) about the legal verdict for me, for I have had unlawful intercourse with a slave-girl who visited me.
So they mentioned it to the Messenger of Allah (ﷺ) saying: We have never seen anyone (so weak) from illness as he is. If we bring him to you, his bones will disintegrate. He is only skin and bone. So the Messenger of Allah (ﷺ) commanded them to take one hundred twigs and strike him once.
In-book : Book 40, Hadith 122
English translation : Book 39, Hadith 4457