In a hadeeth reported by Abu Hurayrah from the Messenger of Allaah (peace and blessings of Allaah be upon him): “Whoever glorifies Allaah (says Subhaan Allaah) thirty-three times immediately after each prayer, and praises Allaah (says Al-hamdu Lillaah) thirty-three times, and magnifies Allaah (says Allaahu akbar) thirty-three times, this makes ninety-nine, then to complete one hundred says Laa ilaaha ill-Allaah wahdahu laa shareeka lahu, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer (There is no god except Allaah Alone, with no partner, His is the power and His is the praise, and He is Able to do all things) – his sins will be forgiven even if they are like the foam of the sea.” (Reported by Muslim, 939)
