3919 The force of "then" is that of finality. The Qur'an is the last Book revealed. Or it may be here to point the contrast between "to thee" in the last verse, i.e., the Prophet, in contradistinction to the People of Islam, who inherited the Book after him. 3920 The custodians of the Qur'an after the Prophet were the People of Islam. They were chosen for the Book, not in any narrow sense, but in the sense that the Book was given for their age and they were charged to obey it and preserve and propagate it, so that all mankind should receive the Message. But it does not follow that they are all true and faithful to their charge, as indeed we see too painfully around us today. Just as mankind was chosen collectively to be Vicegerents for Allah, and yet some among mankind fell into evil-even so, some in the house of Islam fail to follow the Light given to them, and thus "wrong their own souls". But some follow a middle course; in their case "the spirit is indeed willing, but the flesh is weak": their intentions are good, but they have much to learn yet of the true Muslim life and Muslim virtues. Then there is a third class: they may not indeed be perfect, but both their intentions and their conduct are sound, and they form an example to other men: they are "foremost" in every good deed. They are so, not by their own merits, but by the Grace of Allah. And they have reached the highest Achievement-the salvation, which is typified by the various metaphors that follow.