It is narrated from Hazrat Abu Ayyub Ansari (may Allah be pleased with him) that when the Noble Prophet (peace and blessings be upon him) arrived in Madinah Munawwarah, he graced my house with his presence and said to me, "O Abu Ayyub! Shall I not teach you something?" I submitted, "O Messenger of Allah! Certainly." The Noble Prophet (peace and blessings be upon him) said, "Whoever says these words in the morning: 'There is no deity except Allah, He is alone, He has no partner,' then Allah Almighty will write ten good deeds for him in exchange, forgive ten sins for him, or he will have the reward equal to freeing ten slaves, and until the evening these words will become a shield for him against Satan. And whoever says these words in the evening, the same ruling applies to him."