Tafsir Ibn Kathir -> Surah At-Taubah -> Reason behind revealing Ayah 9:74

Al-Amawi said in his Book on Battles, "Muhammad bin Ishaq narrated that Az-Zuhri said that `Abdur-Rahman bin `Abdullah bin Ka`b bin Malik narrated from his father, from his grandfather that he said, `Among the hypocrites who lagged behind ﴿from battle﴾ and concerning whom the Qur'an was revealed, was Al-Julas bin Suwayd bin As-Samit, who was married to the mother of `Umayr bin Sa`d. `Umayr was under the care of Al-Julas. When the Qur'an was revealed about the hypocrites, exposing their practices, Al-Julas said, `By Allah! If this man (Muhammad) is saying the truth, then we are worse than donkeys.' `Umayr bin Sa`d heard him and said, `By Allah, O Julas! You are the dearest person to me, has the most favor on me and I would hate that harm should touch you, more than I do concerning anyone else! You have uttered a statement that if I exposed, will expose you, but if I hide, it will destroy me. One of them is a lesser evil than the other.' So `Umayr went to the Messenger of Allah and told him what Al-Julas said. On realizing this, Al-Julas went to the Prophet and swore by Allah that he did not say what `Umayr bin Sa`d conveyed he said. `He lied on me,' Al-Julas said. Allah sent in his case this verse,

﴿يَحْلِفُونَ بِاللَّهِ مَا قَالُواْ وَلَقَدْ قَالُواْ كَلِمَةَ الْكُفْرِ وَكَفَرُواْ بَعْدَ إِسْلَـمِهِمْ﴾

(They swear by Allah that they said nothing (bad), but really they said the word of disbelief, and they disbelieved after accepting Islam) until the end of Ayah. The Messenger of Allah conveyed this Ayah to Al-Julas, who, they claim, repented and his repentance was sincere, prompting him to refrain from hypocrisy.''' Imam Abu Ja`far Ibn Jarir recorded that Ibn `Abbas said, "The Messenger of Allah was sitting under the shade of a tree when he said,

«إِنَّهُ سَيَأْتِيكُمْ إِنْسَانٌ فَيَنْظُرُ إِلَيْكُمْ بِعَيْنَيِ الشَّيْطَانِ فَإِذَا جَاءَ فَلَا تُكَلِّمُوه»

(A man will now come and will look to you through the eyes of a devil. When he comes, do not talk to him.)' A man who looked as if he was blue (so dark) came and the Messenger of Allah summoned him and said,

«عَلَامَ تَشْتُمُنِي أَنْتَ وَأَصْحَابُك»

(Why do you curse me, you and your companions) That man went and brought his friends and they swore by Allah that they did nothing of the sort, and the Prophet pardoned them. Allah, the Exalted and Most Honored revealed this verse,

﴿يَحْلِفُونَ بِاللَّهِ مَا قَالُواْ﴾

(They swear by Allah that they said nothing (bad)...)