Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:8:49 –

˹Remember˺ when the hypocrites and those in whose hearts was disease said, "Their religion has deluded those ˹Muslims˺." But whoever relies upon Allah - then indeed, Allah is Exalted in Might and Wise.  

When the hypocrites and those in whose hearts is a sickness, a weakness of faith, said, ‘Their religion has deluded them’, that is, the Muslims, for they had set out to fight a large army despite their small number, in the mistaken belief that they will be victorious because of this. God, exalted be He, says in response to them: but whoever relies on God, ˹whoever˺ puts his trust in Him, he will triumph; for truly God is Mighty, His way will prevail, Wise, in His actions.
القرآن:٨:٤٩ –

إِذْ يَقُولُ الْمُنَافِقُونَ وَالَّذِينَ فِي قُلُوبِهِمْ مَرَضٌ غَرَّ هَٰؤُلَاءِ دِينُهُمْ ۗ وَمَنْ يَتَوَكَّلْ عَلَى اللَّهِ فَإِنَّ اللَّهَ عَزِيزٌ حَكِيمٌ  

{إذ يقول المنافقون والذين في قلوبهم مرض} ضعف اعتقاد {غرَّ هؤلاء} أي المسلمين {دينُهم} إذ خرجوا مع قتلهم يقاتلون الجمع الكثير توهما أنهم ينصرون بسببه قال تعال في جوابهم: {ومن يتوكل على الله} يثق به يغلب {فإن الله عزيز} غالب على أمره {حكيم} في صنعه.

See similar narrations below:

Collected by Qurʾān
quran:33:12 –

And ˹remember˺ when the hypocrites and those in whose hearts is disease said, "Allah and His Messenger did not promise us except delusion,"  

And, mention, when the hypocrites, and those in whose hearts is sickness, namely, weakness of conviction, were saying, ‘What God and His Messenger promised us, of assistance ˹to victory˺, was ˹nothing˺ but delusion’, falsehood.
القرآن:٣٣:١٢ –

وَإِذْ يَقُولُ الْمُنَافِقُونَ وَالَّذِينَ فِي قُلُوبِهِمْ مَرَضٌ مَا وَعَدَنَا اللَّهُ وَرَسُولُهُ إِلَّا غُرُورًا  

{و} اذكر {إذ يقول المنافقون والذين في قلوبهم مرض} ضعف اعتقاد {ما وعدنا الله ورسوله} بالنصر {إلا غرورا} باطلا.