Hadith: When you (both) go to your bed say "Allah is the Greatest" thirty-three times "Glory be to Allah" thirty-three times, and "Praise be to Allah" thirty-three times

عن علي بن أبي طالب رضي الله عنه أن رسول الله صلى الله عليه وسلم قال له ولفاطمة: «إذَا أَوَيْتُمَا إِلَى فِرَاشِكُمَا -أَوْ إِذَا أَخَذْتُمَا مَضَاجِعَكُمَا- فَكَبِّرا ثَلاَثًا وَثَلاثِينَ، وَسَبِّحَا ثَلاثًا وَثَلاثِينَ، واحْمِدا ثَلاثًا وَثَلاثِينَ» وفي روايةٍ: التَّسْبيحُ أرْبعًا وثلاثينَ، وفي روايةٍ: التَّكْبِيرُ أرْبعًا وَثَلاَثينَ.
[صحيح] - [متفق عليه. أما رواية أن التسبيح أربع وثلاثون فراوها البخاري]

‘Ali ibn Abi Tālib (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said to him and Fātimah: "When you (both) go to your bed, say "Allah is the Greatest" thirty-three times, "Glory be to Allah" thirty-three times, and "Praise be to Allah" thirty-three times." According to another narration, he said: "Say 'Glory be to Allah' thirty-four times." Another narration reads: "Say 'Allah is the Greatest' thirty-four times.”
Sahih/Authentic. - [Al-Bukhari]

Explanation

Fātimah (may Allah be pleased with her) complained to the Prophet (may Allah's peace and blessings be upon him) of the pain she suffered from using the millstone, and requested from her father a servant. Thereupon, the Prophet (may Allah's peace and blessings be upon him) said to her: "Shall I not tell you of something that is better than a servant?" Then he taught them this Dhikr that is to be said when getting ready to go to bed: "Glory be to Allah" thirty-three times, "Praise be to Allah" thirty-three times, and "Allah is the Greatest" thirty-four times. Then the Prophet (may Allah's peace and blessings be upon him) said: "This is better for you than a servant." Based upon that, it is desirable for a person when he goes to bed to say "Glory be to Allah" thirty-three times, "Praise be to Allah" thirty-three times, and "Allah is the Greatest" thirty-four times; this is a set of one hundred times. This Dhikr helps one fulfill his duties and one sleeps, thus, after remembering Allah, the Almighty.