Riyad as-Salihin: The Book of the Remembrance of Allah – Hadith No. 780 — Ali (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said… (Hadith No. 780)

'Ali (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said to me and to Fatimah (May Allah be pleased with her) (Ali's wife and the Prophet's daughter), "When you go to bed, recite: Takbir (Allahu Akbar) thirty-three times and Tasbih (Subhan-Allah) thirty-three times and Tahmid (Al-hamdu lillah) thirty-three times."Another narration is: The Messenger of Allah (ﷺ) said, "Recite Tasbih thirty-four times."Another narration is: The Messenger of Allah(ﷺ) said, "Recite Takbir thirty-four times.".

Explanation:

Reference: Riyad as-Salihin, The Book of the Remembrance of Allah, Hadith No. 780