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.
tirmidhi:1955[Chain 1] Hannād > Abū Muʿāwiyah > Ibn Abū Laylá [Chain 2] Sufyān b. Wakīʿ > Ḥumayd b. ʿAbd al-Raḥman al-Ruʾāsī > Ibn Abū Laylá > ʿAṭiyyah > Abū Saʿīd > Qāl Rasūl

"Whoever is not grateful to the people, he is not grateful to Allah."  

Abū ʿĪsá said that this Ḥadīth is Ḥasan-Ṣaḥīḥ.
الترمذي:١٩٥٥حَدَّثَنَا هَنَّادٌ حَدَّثَنَا أَبُو مُعَاوِيَةَ عَنِ ابْنِ أَبِي لَيْلَى ح وَحَدَّثَنَا سُفْيَانُ بْنُ وَكِيعٍ حَدَّثَنَا حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ الرُّؤَاسِيُّ عَنِ ابْنِ أَبِي لَيْلَى عَنْ عَطِيَّةَ عَنْ أَبِي سَعِيدٍ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ لَمْ يَشْكُرِ النَّاسَ لَمْ يَشْكُرِ اللَّهَ وَفِي الْبَابِ عَنْ أَبِي هُرَيْرَةَ وَالأَشْعَثِ بْنِ قَيْسٍ وَالنُّعْمَانِ بْنِ بَشِيرٍ  

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ حَسَنٌ صَحِيحٌ