Once, Rasulullah (sallallahu ‘alaihi wasallam) left for Fajr Salaah from the home of his respected wife, Sayyidah Juwairiyyah (radhiyallahu ‘anha). As he left the home, he noticed her seated in her place of salaah, engaged in the zikr of Allah Ta‘ala. Thereafter, when it was midmorning, Rasulullah (sallallahu ‘alaihi wasallam) returned to her home and found that Sayyidah Juwairiyyah (radhiyallahu ‘anha) was still seated in her place of salaah.

Rasulullah (sallallahu ‘alaihi wasallam) thus asked her, “Did you remain in the same condition (engaged in the zikr of Allah Ta‘ala) as you were when I left you?” When she replied that she had indeed remained engaged in zikr for the entire time, Rasulullah (sallallahu ‘alaihi wasallam) said, “After I left, I recited four phrases three times. These phrases are such that if they have to be weighed against all the zikr that you made today, these phrases will outweigh your zikr.”

Rasulullah (sallallahu ‘alaihi wasallam) then taught her the following words:

سُبْحَانَ اللهِ وَبِحَمْدِهِ عَدَدَ خَلْقِهِ وَرِضَا نَفْسِهِ وَزِنَةَ عَرْشِهِ وَمِدَادَ كَلِمَاتِهِ

I proclaim that Allah Ta‘ala is free of any imperfection together with praising Him, equal to the number of His creation, equal to the amount that will please Him, equal to the weight of His throne and equal to His words. (Saheeh Muslim #6913)

Similarly, Rasulullah (sallallahu ‘alaihi wasallam) once entered the home of another of his respected wives, Sayyidah Safiyyah (radhiyallahu ‘anha) and found her seated with four thousand date seeds before her. Rasulullah (sallallahu ‘alaihi wasallam) asked her, “O daughter of Huyayy! What are you doing?” She replied, “I am reciting tasbeeh on these seeds.” Rasulullah (sallallahu ‘alaihi wasallam) responded, “I have recited more tasbeeh than that since I entered and stood next to you.”

Sayyidah Safiyyah (radhiyallahu ‘anha) was eager to learn how she could also gain the reward of such abundant tasbeeh in so little time and thus beseeched Rasulullah (sallallahu ‘alaihi wasallam), “Teach me, O Rasul of Allah (sallallahu ‘alaihi wasallam)!” Rasulullah (sallallahu ‘alaihi wasallam) replied, “Recite the following:

سُبْحَانَ اللهِ عَدَدَ مَا خَلَقَ مِنْ شَيْءٍ

I proclaim that Allah Ta‘ala is free of any imperfection equal to the number of His creation. (Mustadrak Haakim #2008)

(Also see: Sunan Tirmizi #3554 and Nataa-ijul Afkaar vol. 1, pg. 81)