ENOfficial
Abu Huraira reported God's Messenger as saying, “He who does not thank people does not thank God.” Ahmad and Tirmidhi transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ لَمْ يَشْكُرِ النَّاسَ لَمْ يَشْكُرِ اللَّهَ» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيُّ
sunnah.com