Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) came to Madinah and stayed with Abu Ayyub. The Messenger of Allah (peace and blessings be upon him) was lodged on the lower floor, and Abu Ayyub stayed on the upper floor. When evening came and they settled in for the night, Abu Ayyub began to think that he was on the roof of the house of the Messenger of Allah (peace and blessings be upon him) with him below, and that he was between him and the revelation. So Abu Ayyub could not sleep, fearing that dust might fall on him and that he would move and cause him discomfort. When morning came, he went early to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah! Neither I nor Umm Ayyub closed our eyes all night. He (peace and blessings be upon him) said: "O Abu Ayyub! What was the reason for that?" He said: I remembered that I am on the roof of the house and you are below me; when I move, dust scatters on you, and my moving causes you discomfort, while I am between you and the revelation. He (peace and blessings be upon him) said: "O Abu Ayyub! Do not do that. Shall I not teach you some words which, if you say them ten times in the morning and ten times in the evening, you will be given ten good deeds for them, ten of your sins will be wiped away, you will be raised ten degrees, and on the Day of Resurrection they will be for you equal to freeing ten slaves? Say: 'La ilaha illallah, lahul-mulku wa lahul-hamdu, la sharika lah' (There is no god but Allah; His is the dominion and His is the praise; He has no partner)."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3971