THE VIRTUES OF ZIKR

Hadhrat Umm-e-Haani (Radiyallahu anha) narrates that once Rasulullah (Sallallaahu ‘Alaihi Wasallam) visited her and she said to him: "O Rasulullah (Sallallaahu ‘Alaihi Wasallam), I have become old and weak. Teach me an act that I can perform while sitting.”
Rasulullah (Sallallaahu ‘Alaihi Wasallam) said to her: “Recite سُبْحَانَ اللّٰهِa hundred times; its reward is as if you freed a hundred Arab slaves. Recite اَلْحَمْدُ لِلّٰهِa hundred times; its reward is as if you provided a hundred fully equipped horses (with saddles, reins, and loaded with other equipement) in the way of Allah (i.e. for Jihad). Recite اَللّٰهُ أَكْبَرُ a hundred times; its reward is as if you sacrificed a hundred camels which Allah has accepted. And recite لَا اِلٰهَ اِلَّا اللّٰهُ a hundred times; its reward will fill the space between the heavens and the earth. There is no act that can surpass it.”

 [English version of "Les vertus du zikr" – Al Haadi – Vol. 3 No. 1]