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:6116 – Bakr b. Muḥammad al-Ṣayrafī Bimarw > ʿAbd al-Ṣamad b. al-Faḍl > Makkī b. Ibrāhīm > Hāshim b. Hāshim > ʿĀmir b. Saʿd from his father

[Machine] I have seen myself as one-third of Islam.  

الحاكم:٦١١٦ – أَخْبَرَنَا بَكْرُ بْنُ مُحَمَّدٍ الصَّيْرَفِيُّ بِمَرْوَ ثَنَا عَبْدُ الصَّمَدِ بْنُ الْفَضْلِ ثَنَا مَكِّيُّ بْنُ إِبْرَاهِيمَ أَخْبَرَنِي هَاشِمُ بْنُ هَاشِمٍ عَنْ عَامِرِ بْنِ سَعْدٍ عَنْ أَبِيهِ قَالَ

«لَقَدْ رَأَيْتُنِي وَأَنَا لَثُلُثُ الْإِسْلَامِ» صحيح  

See similar narrations below:

Collected by Bukhārī
bukhari:3726 – Makkī b. Ibrāhīm > Hāshim b. Hāshim > ʿĀmir b. Saʿd from his father > Laqad Raʾaytunī

No doubt, (for some time) I stood for one-third of the Muslims.  

البخاري:٣٧٢٦ – حَدَّثَنَا مَكِّيُّ بْنُ إِبْرَاهِيمَ حَدَّثَنَا هَاشِمُ بْنُ هَاشِمٍ عَنْ عَامِرِ بْنِ سَعْدٍ عَنْ أَبِيهِ قَالَ

لَقَدْ رَأَيْتُنِي وَأَنَا ثُلُثُ الإِسْلاَمِ