Abu Dawud Book 36, Hadith Number 5051.

Chapter : Not known.

Narated By Anas ibn Malik : The Prophet (PBUH) said: If anyone says in the morning or in the evening: “O Allah! in the morning we call Thee, the bearers of Thy Throne, Thy angels and all Thy creatures to witness that thou art Allah (God) than Whom alone there is no god, and that Muhammad is Thy Servant and Apostle,” Allah will emancipate his fourth from Hell; if anyone says twice, Allah will emancipate his half; if anyone says it thrice, Allah will emancipate three-fourth; and if he says four times, Allah will emancipate him from Hell.