Kaab reported,

When the Quran was revealed mentioning the hypocrites and what the Messenger of Allah ﷺ had said, Jalas remarked, "By Allah, if this man is truthful, then we are worse than donkeys."Umayr bin Saad heard him say this and responded, "By Allah, Jalas, you are the dearest of people to me, the one who has done me the most good, and the one I would least wish to see harmed by anything he dislikes. But you have spoken words which, if I report them, will disgrace you, and if I keep silent about them, will destroy me. One of these two outcomes is worse for me than the other."So he went to the Messenger of Allah ﷺ and told him what Jalas had said. Jalas swore by Allah that he had not said what Umayr claimed and that Umayr had lied about him. Then Allah revealed, "They swear by Allah that they said nothing, but they did say the word of disbelief, and disbelieved after their submission" [Tawbah 9:74].

عن كعب قال

لما نزل القرآن، فيه ذكر المنافقين وما قال رسول الله ﷺ، قال الجلاس: والله! لئن كان هذا الرجل صادقا لنحن أشر من الحمير، قال: فسمعها عمير بن سعد، فقال: والله يا جلاس إنك لأحب الناس إلي، أحسنهم عندي أثرا أو أعزهم علي أن يدخل عليه شيء يكرهه، ولقد قلت مقالة لئن ذكرتها لتفضحنك، ولئن سكت عنها لتهلكني، ولأحدهما أشر علي من الأخرى، فمشى إلى رسول الله ﷺ، فذكر له ما قال الجلاس، فحلف بالله ما قال [ما قال] عمير، ولقد كذب علي، فأنزل الله: {يحلفون بالله ما قالوا ولقد قالوا كلمة الكفر وكفروا بعد إسلمهم}