O you who have believed, this is a address to the Muslims. The meaning of 'have believed' is to remain steadfast in faith, to continue in it, and to increase it. And the Book that was sent down before refers to the genre of what was sent down to the prophets before him from the books. The evidence for this is his saying: 'and His books.' It was read as 'and His Book' intending the genre. It was also read as 'sent down.'

And 'sent down' is in the active voice. It was said that the address is to the People of the Book, because they believed in some books and messengers and disbelieved in others. It was narrated that this was about Abdullah ibn Salam, and Asad and Asid, the sons of Ka'b, and Thalabah ibn Qais, and Salam, the nephew of Abdullah ibn Salam, and Salmah, his cousin, and Yamin ibn Yamin. They came to the Messenger of Allah, blessings and peace be upon him, and said: 'O Messenger of Allah, we believe in you and in your Book, and in Musa and the Torah, and in Uzair, and we disbelieve in what is besides that from the books and messengers.' He, peace be upon him, said: 'Rather, believe in Allah and His Messenger Muhammad and His Book, the Qur'an, and in every Book that was before it.' They said: 'We will not do that,' so it was revealed, and they all believed. [This was mentioned by Al-Thaalibi from the narration of Al-Kalbi from Abu Salih from Ibn Abbas. Al-Wahidi mentioned it in the causes from Al-Kalbi without a chain.]

It was said that it is for the hypocrites, as if it was said: O you who have believed in hypocrisy, believe sincerely. If you say: How was it said to the People of the Book (and the Book that was sent down before) while they believed in the Torah and the Gospel? I say: They believed in them only, and they did not believe in all that was sent down from the books. So they were commanded to believe in the whole genre, and because their belief in some books does not constitute true belief in it, because the way to believe in it is through the miracle, and there is no exclusivity of miracles to some books over others. If their belief was based on the miracle, they would have believed in all of it. So when they believed in some of it, it was known that they did not consider the miracle, thus their belief was not true belief. This is what Allah, glorified and exalted is He, intended in His saying: (And they say, 'We believe in some and disbelieve in others,' and they wish to adopt a way in between. Those are the true disbelievers.) If you say: Why was it said (sent down upon His Messenger) and (sent down before)? I say: Because the Qur'an was sent down in parts over twenty years, unlike the books before it. And the meaning of His saying: 'And whoever disbelieves in Allah...' is: And whoever disbelieves in anything of that has certainly gone astray, because disbelief in some is disbelief in all. Do you not see how the command to believe in all of it was given precedence?