Abu Dawud Book 36, Hadith Number 5055.

Narated By Abdullah ibn Ghannam : The Prophet (PBUH) said: If anyone says in the morning: “O Allah! whatever favour has come to me, it comes from Thee alone Who has no partner; to Thee praise is due and thanksgiving,’! he will have expressed full thanksgiving for the day; and if anyone says the same in the evening, he will have expressed full thanksgiving for the night.