Sahih Bukhari

The Prophet (ﷺ) said, "Whoever said "None has the right to be worshippedbut Allah and has in his heart good (faith) equal to the weight of abarley grain will be taken out of Hell. And whoever said: "None hasthe right to be worshipped but Allah and has in his heart good (faith)equal to the weight of a wheat grain will be taken out of Hell. Andwhoever said, "None has the right to be worshipped but Allah and hasin his heart good (faith) equal to the weight of an atom will be takenout of Hell."