Musnad Ahmad 25:999

'Abd al-Razzaq narrated to us, he said: Ma'mar informed us, from al-Zuhri, from 'Ubayd Allah ibn 'Abd Allah ibn 'Utbah, from Ibn 'Abbas, from the Messenger of Allah, peace and blessings of Allah be upon him, who said: "Gabriel recited to me upon one mode, so I requested him to increase it, and I did not cease asking him to increase it, and he would increase it, until it reached seven modes." Al-Zuhri said: "And these modes are only regarding the one matter; there is no difference in what is lawful or what is unlawful."