51. That is, they do not live a carefree life devoid of the fear of God. They live in awe of Him and are fully conscious that He oversees and watches them in all their motives and actions and they are thus deterred from thinking and doing evil.
52. Signs here means both divine revelations to the Prophets and the signs found in man’s own self and in the universe around him. To believe in the verses of the Book is to affirm them, and to believe in the signs of human self and the universe is to affirm the realities which they point to.
53. Though belief in the revelations itself ingrains the doctrine of Tauhid in the hearts, yet the believers have been warned to guard against shirk. This is because, in spite of believing in the revelations, man is inclined to commit shirk in one form or the other, for instance, in exaggerating the teachings of the Prophets and righteous people, supplicating and serving others than Allah, etc.
54. This verse (60) may be elaborated like this: They serve their Lord and try their best to obey Him and do righteous deeds, but all along they remain humble in their hearts and are not puffed up with the pride of their piety. Nay, in spite of all their good deeds, their hearts are always filled with awe that they shall have to render an account to their Lord, and they are not sure whether they will come out successful in the judgment of their Lord or not. A concrete interpretation of this verse is afforded by Umar. Although he served his Allah in a way that was exemplary, yet he was so afraid of accountability to Him that he is reported to have said before death: I shall consider it a favor, if I am neither rewarded nor punished in the Hereafter. Hasan Basri has expressed the same thing in a beautiful manner: A believer obeys Allah and is yet fearful of Him, and a hypocrite disobeys Allah and is yet fearless of Him.