We were commanded to glorify Allah after every prayer thirty-three times, to praise Him thirty-three times, and to magnify Him thirty-four times.Then a man from the Ansar saw in a dream someone who asked him, "Did the Messenger of Allah ﷺ command you to glorify Allah thirty-three times after every prayer, to praise Allah thirty-three times, and to magnify Him thirty-four times?"He replied, "Yes."The figure said, "Make them twenty-five each, and add the declaration of Allah's oneness along with them."In the morning he came to the Prophet ﷺ and told him about it, and the Prophet ﷺ said, "Do so."
أمرنا أن نسبح دبر كل صلاة ثلاثا وثلاثين، وتحمده ثلاثا وثلاثين، وتكبره أربعا وثلاثين، قال: فرأى رجل من الأنصار في المنام فقال: أمركم رسول الله ﷺ أن تسبحوا في دبر كل صلاة ثلاثا وثلاثين، وتحمدوا الله ثلاثا وثلاثين، وتكبروا أربعا وثلاثين؛ قال: نعم، قال: فاجعلوا خمسا وعشرين، واجعلوا التهليل معهن، فغدا على النبي ﷺ فحدثه فقال: افعلوا.
Tirmidhi (3413), Nasai (1350), and Ahmad (21600) all narrated it, and Ibn Khuzayma (752) and Ibn Hibban (2017) graded it sahih, all of them through the route of Hisham bin Hassan, from Muhammad bin Sirin, from Kathir bin Aflah, from Zayd bin Thabit, who related it in the same manner. Tirmidhi said, "This is a sahih hadith." And it is as he said.As for the statement, "make it twenty-five," it means that the tasbih is twenty-five, the tahmid is twenty-five, the takbir is twenty-five, and "there is no god but Allah" is twenty-five, making a total of one hundred. And "dubur" here means right after the prayer.