1) Allaah the Most High says: Those who believe and do not mix their belief with dhulm, they are those upon whom is security and they are the rightly guided. [6:82]
From 'Abdullaah ibn Mas'ood, who said: When this verse was revealed, some Muslims began to grieve, and said: 'Which of us does not do dhulm (oppression) to his soul?' The Messenger of Allaah said: "It is not that, verily it is shirk, have you not heard the saying of Luqmaan to his son: Oh my Son! Do not make shirk with Allaah. Verily, shirk is a great dhulm.[31:13] [Bukhari & Muslim]
This verse gives glad tidings to the believers, those who single out Allaah alone for worship, those who do not mix their belief with shirk. Rather, they are far from it, they have complete security from the punishment of Allaah in the Hereafter and they are the rightly guided in this world.
2) The Prophet said: "Imaan consists of sixty something branches, the highest of them is the saying 'Laa ilaaha illa Allaah; and the lowest of them is to remove something harmful from the road." [Muslim]
3) Shaikh 'Abdullaah Khayaat mentions in his book entitled Daleel ul-Muslim Fil I'tiqaad wat-Tat-heer. "Because of the human nature of man and due to his lack of infallibility, his feet slip and he falls into disobedience to Allaah.
