Musannaf Ibn Abi Shayba 21:164

Muhammad ibn Bishr narrated to us, Mis'ar narrated to us, from Bukayr ibn al-Akhnas, who said: Whoever says when he enters the evening and when he enters the morning, three times: "O Allah, I have entered the evening bearing witness," and when he enters the morning he says: "O Allah, I have entered the morning bearing witness that whatever wellness or blessing has come to us is from You alone, You have no partner, so to You is the praise," he will not be asked about any blessing that was in that night of his or that day of his, except that he has fulfilled its gratitude.