Is there any backup for this statement about the virtue of Ramadan?

Often at the end of the month sha'aban or during Ramadan in speeches the Imams use this statement to show the importance or virtue of the month of Ramadan saying: > هو شهر أولـــــه رحمـــــة وأوسطـه مغفـرة وآخـــــره عتـــق مــــــن النار one may translate it: > It is a month whose beginning is mercy, its middle is forgiveness and its end is ransom from the Fire does this statement has any backup in the sunnah? If so with which qualification?