Praise be to Allah.
This hadith was narrated from a number of the Sahaabah (may Allah be pleased with them):
The first hadith was narrated from Ibn ‘Umar (may Allah be pleased with him). This version says: “Three will be on hills of musk on the Day of Resurrection: a slave who fulfilled his duty towards his Lord and towards his masters; a man who led people in prayer when they were pleased with him; and a man who called people to the five daily prayers, every day and night.”
This report was narrated from him via two chains of narration (isnaads):
The first isnaad is: it was narrated by Imam Ahmad in al-Musnad (2/26), al-Bukhaari in at-Taareekh al-Kabeer (6/105), at-Tirmidhi in al-Jaami‘ (1986), at-Tabaraani in al-Mu‘jam al-Awsat (1/129), Abu Nu‘aym in Hilyat al-Awliyaa’ (9/320), and al-Bayhaqi in Shu‘ab al-Eemaan (4/451). All of them narrated it via Abu’l-Yaqzaan, from Zaadaan, from ‘Abdullah ibn ‘Umar in a marfoo‘ report (attributed to the Prophet (blessings and peace of Allah be upon him)).
This isnaad is da‘eef (weak) because of Abu’l-Yaqzaan, whose name was ‘Uthmaan ibn Qays. Yahya ibn Ma‘een said concerning him: His hadith is nothing. Abu Haatim said: His hadith is da‘eef (weak) and munkar (odd). Ad-Daaraqutni said: [He is] matrook (to be rejected).
See: Tahdheeb at-Tahdheeb (7/146).
The second isnaad is: It was narrated by at-Tabaraani in al-Mu‘jam al-Kabeer (12/433), Abu Nu‘aym in Hilyat al-Awliya’ (3/318) and others, via:
Al-Haarith ibn Muslim: Bahr ibn Katheer told us, from al-Hajjaaj ibn Faraafisah, from al-A‘mash, from ‘Ataa’, from Ibn ‘Umar. This isnaad is also da‘eef jiddan (very weak), because of Bahr ibn Katheer as-Saqqa. adh-Dhahabi said of him in ad-Du’afaa’ (1/192): He was one of those who reached a point where mistakes became very serious and he became very confused, to the extent that he deserved to be rejected. End quote.
The second hadith was narrated from Abu Hurayrah and Abu Sa‘eed al-Khudri (may Allah be pleased with them both). The wording of their hadith is:
“There are three who will be on a hill of black musk on the Day of Resurrection; the terror [of the Day of Resurrection) will not scare them, and they will not be subjected to the reckoning. [They are:] a man who recited Qur’an, seeking the Countenance of Allah, and led people in prayer by reciting it when they were pleased with him; a man who gave the adhaan in a mosque, calling people to Allah, seeking the Countenance of Allah; and a man who was tested by being enslaved in this world, but that did not distract him from seeking the hereafter.”
This was narrated by al-Bayhaqi in Shu‘ab al-Eemaan (3/382) and al-Khateeb in Taareekh Baghdad (3/355), via al-Fadl ibn Maymoon as-Sulami, from Mansoor ibn Zaadhaan, from Zaadhaan Abu ‘Umar al-Kindi, who said: I heard Abu Sa‘eed and Abu Hurayrah (may Allah be pleased with them)…
This is also a da‘eef jiddan (very weak) isnaad, as it includes al-Fadl ibn Maymoon. In his biography in Lisaan al-Mizaan (4/451) it says:
Al-Fadl ibn Maymoon, Abu Salamah, a shaykh of ‘Aarim. Abu Haatim said: His hadith is munkar (odd). He heard from Mu‘aawiyah ibn Qurrah and others. Ibn al-Madeeni said: He was always regarded as da‘eef by us. End quote.
He was classed as da‘eef by ad-Daaraqutni in al-‘Ilal, and by Abu Nu‘aym al-Asbahaani, and others. End quote.
Conclusion: this hadith is not soundly narrated from the Prophet (blessings and peace of Allah be upon him).
A number of imams and scholars stated that it is da‘eef, such as Imam al-Bukhaari (may Allah have mercy on him) in at-Taareekh (6/105); ad-Daaraqutni in al-‘Ilal (13/159); Ibn ‘Asaakir in Mu’jam ash-Shuyookh (2/147); Ibn Hajar in Nataa’ij al-Afkaar (1/319)l and Shaykh al-Albaani in as-Silsilah ad-Da‘eefah (6812). It was also classed as da‘eef by the commentators on Musnad al-Imam Ahmad, Mu’sasat ar-Risaalah edn. (8/418).
With regard to the content of the hadith, it mentions the virtues of three noble deeds, and the virtues of the deeds referred to do not depend only on this da‘eef hadith; rather the reward for these deeds is confirmed in other evidence and reports:
With regard to leading the prayer, Shaykh Saalih al-Fawzaan (may Allah preserve him) said: This is an important religious role that the Messenger of Allah (blessings and peace of Allah be upon him) himself undertook, as did the Rightly-Guided Caliphs who succeeded him.… Hence some of the Sahaabah (may Allah be pleased with them) would say to the Prophet (blessings and peace of Allah be upon him): Appoint me as the imam of my people, because they knew of the great virtue and reward that there is in that. But unfortunately, nowadays we see that many seekers of knowledge are not keen to lead the prayers; they have no interest in it and are reluctant to do it, preferring to be lazy and show little interest in doing good. This stems only from the discouragement of the Shaytaan. The right thing to do is to take it upon themselves with keenness, seeking reward with Allah, for it is more expected of seekers of knowledge that they should do this and other righteous deeds. End quote.
Al-Mulakhkhas al-Fiqhi (1/215-216).
With regard to the adhaan, we have explained its virtue previously in the answer to question no. 70472.
With regard to a slave treating his masters well, it was narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: “If a slave fulfils his duty towards Allah and his duty towards his masters, he will have two rewards.” Narrated by Muslim (1666).
And Allah knows best.