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
hakim:4950 – Abū Jaʿfar al-Rāzī al-Baghdādī > Abū ʿUlāthah from my father > Ibn Lahīʿah > Abū al-Aswad > ʿUrwah

[Machine] "The first person to embrace Islam was Zaid bin Harithah."  

الحاكم:٤٩٥٠ – حَدَّثَنَا أَبُو جَعْفَرٍ الرَّازِيُّ الْبَغْدَادِيُّ ثنا أَبُو عُلَاثَةَ ثنا أَبِي ثنا ابْنُ لَهِيعَةَ عَنْ أَبِي الْأَسْوَدِ عَنْ عُرْوَةَ

«أَنَّ أَوَّلَ مَنْ أَسْلَمَ زَيْدُ بْنُ حَارِثَةَ»  

See similar narrations below:

Collected by Ṭabarānī, Suyūṭī
tabarani:4653 – Abū Shuʿayb al-Ḥarrānī > Saʿīd b. Abū Maryam > Ibn Lahīʿah > Ibn Shihāb

[Machine] The first person to convert to Islam was Zaid ibn Haritha.  

الطبراني:٤٦٥٣ – حَدَّثَنَا أَبُو شُعَيْبٍ الْحَرَّانِيُّ ثنا سَعِيدُ بْنُ أَبِي مَرْيَمَ ثنا ابْنُ لَهِيعَةَ عَنِ ابْنِ شِهَابٍ قَالَ

«أَوَّلُ مَنْ أَسْلَمَ زَيْدُ بْنُ حَارِثَةَ»