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
suyuti:2077a –

“If a person prays in public and does it well, and he prays in secret and does it well, then Allah says: ‘This man is truly My slave.’” (Using translation from Ibn Mājah 4200)   

السيوطي:٢٠٧٧a –

"إذا صلَّى العبُد في العلانيةِ (فأحسْنَ) ، وصلى في السرِّ فأحسن، قال الله تعالى: أحسن عبدى".  

الرافعي عن أبي هريرة

See similar narrations below:

Collected by Ibn Mājah, Suyūṭī
ibnmajah:4200 – Kathīr b. ʿUbayd al-Ḥimṣī > Baqiyyah > And Rqāʾ b. ʿUmar > ʿAbdullāh b. Dhakwān Abū al-Zinād > al-Aʿraj > Abū Hurayrah

“If a person prays in public and does it well, and he prays in secret and does it well, then Allah says: ‘This man is truly My slave.’”  

ابن ماجة:٤٢٠٠ – حَدَّثَنَا كَثِيرُ بْنُ عُبَيْدٍ الْحِمْصِيُّ حَدَّثَنَا بَقِيَّةُ عَنْ وَرْقَاءَ بْنِ عُمَرَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ ذَكْوَانَ أَبُو الزِّنَادِ عَنِ الأَعْرَجِ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْعَبْدَ إِذَا صَلَّى فِي الْعَلاَنِيَةِ فَأَحْسَنَ وَصَلَّى فِي السِّرِّ فَأَحْسَنَ قَالَ اللَّهُ ﷻ هَذَا عَبْدِي حَقًّا  

suyuti:5722a –

“If a person prays in public and does it well, and he prays in secret and does it well, then Allah says: ‘This man is truly My slave.’” (Using translation from Ibn Mājah 4200)   

السيوطي:٥٧٢٢a –

"إِنَّ الْعَبْدَ إِذَا صَلَّى في الْعَلانِيَة فَأحْسَنَ، وَصَلَّى فِي السِّر فَأَحْسَن قَال اللهُ ﷻ: هَذَا عَبْدِي حقًّا".  

[هـ] ابن ماجة عن أَبي هريرة