(Note) al-Suyūṭī attributed the ḥadīth to al-Tirmidhī, Ibn Mājah, and al-Ḥākim from ʿUqbah, and al-Munāwī criticized it due to Bakr ibn Yūnus. He attributed it to "Ṭab and al-Mustadrak," but I did not see it there except from the ḥadīth of ʿAbd al-Raḥmān ibn ʿAwf as previously mentioned. And Allāh knows best.

"When a servant fulfills the right of Allāh and the right of his masters, he will have a double reward." It was recorded by Muslim (5/94-95) and Aḥmad (2/252) through the route of Abū Muʿāwiyah from al-Aʿmash from Abū Ṣāliḥ from Abū Hurayrah, raised [to the Prophet], and I narrated it to Kaʿb, who said: "There is no reckoning upon him nor upon a devout believer." It was also narrated by others than Abū Muʿāwiyah with the wording: "How excellent is one of them who perfects the worship of his Lord and advises his master." It was recorded by al-Bukhārī (5/134) through the route of Abū Usāmah from al-Aʿmash, who said: "Abū Ṣāliḥ narrated to us from Abū Hurayrah, raised [to the Prophet]." Aḥmad also recorded it (2/390) through the route of Isrāʾīl from al-Aʿmash with the wording: "How excellent is the servant when he fulfills the right of Allāh and the right of his masters," and added: Kaʿb said: "Allāh and His Messenger have spoken the truth; there is no reckoning upon him nor upon a devout believer." It has another route with the wording: "How excellent is the servant who dies having perfected the worship of Allāh and the companionship of his master; how excellent for him." It was recorded by Muslim (5/95) through the route of ʿAbd al-Razzāq, who said: "Maʿmar narrated to us from Hammām ibn Munabbih from him." Aḥmad also recorded it (318).