The Book of Menstruation (Kitab Al-Haid)
Muslim :: Book 3 : Hadith 699
This hadith is narrated by Muhammad b. 'Amr b. Ata' with these words: I was with Ibn 'Abbas, and Ibn 'Abbas saw the Apostle of Allah (may peace be upon him) doing like this, and it is also said that the words are: He (the Holy Prophet) offered prayer; and the word" people" is not mentioned.