It is narrated from Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever says: 'There is no true god except Allah, alone, He has no partner; His is the dominion and His is all praise, and He has power over all things,' it is equal to freeing four persons from the descendants of Isma'il (peace be upon him)."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4008