The verses maintain that the Quran itself is a "clear proof" of God's signs, and challenge the disbelievers to produce another scripture, or "some vestige of knowledge", to justify their rejection. Verse ten describes a "witness from the Children of Israel" who accepted the revelation. Most Quranic commentators believe that this verse—unlike most of the chapter—was revealed in Medina and the witness refers to Abdullah ibn Salam, a prominent Jew of Medina who converted to Islam, and whom Muhammad was reported to have described as one of the "People of Paradise". A minority—who believe that this verse was revealed in Mecca–say that the witness is Moses who accepted the Torah. Verses 13 and 14 talks about the believers who "stand firm", to whom "no fear shall come ... nor shall they grieve". The exegete Fakhr al-Din al-Razi (1149–1209) says that this means that the believers will not have to fear punishment or many other trials on the Day of Judgement. The believers are described as "those who say 'Our Lord is God'", without specific references to Islam, possibly meaning that this includes the adherents of all Abrahamic religions. This is related to verse 69 of Al-Ma'ida which says that "those who are Jews, and the Christians, and the Sabians—whosoever believes in God and the Last Day and works righteousness" will be rewarded by God, and on them "no fear shall come ... nor shall they grieve". Verses 15 to 17 instruct Muslims to be virtuous (ihsan) towards their parents and do not disobey them. A passage in verse 15 notes that a mother works hard for a period of "thirty months", bearing and nursing her child; the explicit mention of "thirty months" has implications for the calculation of the fetal viability threshold in Islamic law (see #Fetal viability below). Verses 21 to 25 contain the story of the Islamic prophet Hud, who was sent to the people of ʿĀd "by the sand dunes" (Arabic: fi al-Ahqaf, hence the name of the chapter). The people rejected his message and were then punished by a storm that destroyed them. The next verses warn the polytheists of Quraysh—who opposed Muhammad's message of Islam—that they could also be destroyed just as the people of ʿĀd had been destroyed. The last verse (35) is addressed to Muhammad and instructs him to be patient in the face of rejections of his message, just as the previous