Of the reported Adhkar (invocations and Remembrances said at certain times on a regular basis) upon going to sleep is what has been authentically reported in Sahih Al Bukhari and Sahih Muslim on the authority of `Ali ibn Abu Talib (may Allah be pleased with him) that Fatimah (may Allah be pleased with her) came to the Prophet (peace be upon him) asking him to give her a servant, thereupon he said: "May I inform you of something better than that? When you go to bed, say "Subhan Allah" thirty three times, "Alhamdulillah" thirty three times, and "Allahu Akbar" thirty four times. Ali (may Allah be pleased with him) said: "I have never failed to recite it ever since." Somebody asked: "Even on the night of the Battle of Siffin?" He said: "No, even on the night of the battle of Siffin." [Sahih Al Bukhari No. (5362) and Sahih Muslim No. (2727)].
Fatimah, the daughter of the Messenger of Allah (peace be upon him), complained to the Messenger of Allah (peace be upon him) the trouble she suffered of flouring, watering, and service, therefore she asked for a servant to alleviate the hardship she found due to these hard works. Thereupon, the Messenger of Allah (peace be upon him) guided her to something better than a servant when he said: "May I inform you of something better than that?" i.e. better than a servant. This is a perfect advice and suspense. When herself was ready to know the matter which is better for her than a servant, she came to ask him. Then the Messenger of Allah (peace be upon him) said to her: "When you go to bed, say "Subhan Allah" thirty three times, "Alhamdulillah" thirty three times, and "Allahu Akbar" thirty four times." i.e., when you go to sleep, you say these words to complete the number one hundred.
Fatimah (may Allah be pleased with her) rejoiced much for this great news which the Prophet guided her to and her husband Ali (may Allah be pleased with him) rejoiced to that as well to the extent that he said: "I have never failed to recite it ever since." In another narration, he said: "I have never left them since I heard them from the Messenger of Allah (peace be upon him)." It was said to him: "Not even on the night of the Battle of Siffin?" The Battle of Siffin is the famous Battle that took place near Al Forat river between him and the people of the Levant (the region covering Syria, Lebanon, Jordan, and Palestine). Thereupon, he (may Allah be pleased with him) said: "Not even on the night of the Battle of Siffin?" It is well-known that a person may neglect some matters which he used to do or say in the times of hardship, however Ali (may Allah be pleased with him) did not leave reciting these words even in that night, which indicates perseverance, paying attention, and keenness.
The people of knowledge have used this Hadith as a proof to the great virtues and benefits of Adhkar because it gives the one who says so strength in body, health, activity, and spiritual energy. Ibn Al Qayyim (may Allah bestow mercy on his soul) said about that: "Remembrance of Allah gives a person power that a person shall not get but when he says it. I have seen the amazing power of the Shaykh of Islam Ibn Taymiyah in his walk, speech, bravery, and writing." Then, he mentioned the above-mentioned Hadith and commented: "It was said whoever says that frequently shall find power in his body to suffice him of having a servant." Al Wabil As-Sayyib (p. (155-156).
Ibn Al Qayyim (may Allah bestow mercy on his soul) reported from the Shaykh of Islam Ibn Taymiyah that he said: "We have heard that who keeps on saying these words will not find weakness due to work and others." Al Wabil As-Sayyib (p. 206).
We ask Allah to guide us all to every good deed, for He is All-Hearing, All-Responding.