Abu Dawud Book 33, Hadith Number 4458.

Narated By Ali ibn AbuTalib : A slave-girl belonging to the house of the Apostle of Allah (PBUH) committed fornication. He (the Prophet) said: Rush up, Ali, and inflict the prescribed punishment on her. I then hurried up, and saw that blood was flowing from her, and did not stop. So I came to him and he said: Have you finished inflicting (punishment on her)? I said: I went to her while her blood was flowing. He said: Leave her alone till her bleeding stops; then inflict the prescribed punishment on her. And inflict the prescribed punishment on those whom your right hands possess (i.e. slaves).