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:3:169 –

And never think of those who have been killed in the cause of Allah as dead. Rather, they are alive with their Lord, receiving provision,  

The following was revealed regarding martyrs: Count not those who were slain (read qutilū or quttilū) in God’s way, that is, for the sake of His religion, as dead, but rather, that they are, living with their Lord, their spirits inside green birds that take wing freely wherever they wish in Paradise, as reported in a hadīth); provided for ˹by Him˺, with the fruits of Paradise.
القرآن:٣:١٦٩ –

وَلَا تَحْسَبَنَّ الَّذِينَ قُتِلُوا فِي سَبِيلِ اللَّهِ أَمْوَاتًا ۚ بَلْ أَحْيَاءٌ عِنْدَ رَبِّهِمْ يُرْزَقُونَ  

{ولا تحسبن الذين قتلوا} بالتخفيف والتشديد {في سبيل الله} أي لأجل دينه {أمواتا بل} هم {أحياءٌ عند ربهم} أرواحهم في حواصل طيور خضر تسرح في الجنة حيث شاءت كما ورد في الحديث {يرزقون} يأكلون من ثمار الجنة.

See similar narrations below:

Collected by Ḥākim
hakim:3457 – Abū Bakr Muḥammad b. Aḥmad b. Bālawayh > Muḥammad b. Aḥmad b. al-Naḍr al-Azdī > Muʿāwiyah b. ʿAmr > Abū Isḥāq al-Fazārī > Sufyān > Ismāʿīl b. Abū Khālid > Saʿīd b. Jubayr > Ibn ʿAbbās

[Machine] This verse was revealed about Hamza and his companions: "And do not think of those who have been killed in the cause of Allah as dead. Rather, they are alive with their Lord, receiving provision." [Quran 3:169]  

الحاكم:٣٤٥٧ – حَدَّثَنِي أَبُو بَكْرٍ مُحَمَّدُ بْنُ أَحْمَدَ بْنِ بَالَوَيْهِ ثنا مُحَمَّدُ بْنُ أَحْمَدَ بْنِ النَّضْرِ الْأَزْدِيُّ ثنا مُعَاوِيَةُ بْنُ عَمْرٍو ثنا أَبُو إِسْحَاقَ الْفَزَارِيُّ عَنْ سُفْيَانَ عَنْ إِسْمَاعِيلَ بْنِ أَبِي خَالِدٍ عَنْ سَعِيدِ بْنِ جُبَيْرٍ عَنِ ابْنِ عَبَّاسٍ قَالَ

نَزَلَتْ هَذِهِ الْآيَةُ فِي حَمْزَةَ وَأَصْحَابِهِ {وَلَا تَحْسَبَنَّ الَّذِينَ قُتِلُوا فِي سَبِيلِ اللَّهِ أَمْوَاتًا بَلْ أَحْيَاءٌ عِنْدَ رَبِّهِمْ} [آل عمران 169]  

«هَذَا حَدِيثٌ صَحِيحٌ عَلَى شَرْطِ الشَّيْخَيْنِ وَلَمْ يُخْرِجَاهُ» على شرط البخاري ومسلم