Ibn Majah

Hadith Commentary: Benefits and Issues: ➊
The title of the king of Abyssinia is "Najashi."
And every king of Abyssinia was called Najashi.
And the Najashi who became Muslim and died during the lifetime of the Prophet sallallahu alayhi wa sallam was Ashamah, whose death occurred in Rajab, 9 AH.

➋
This hadith proves that if a person passes away whose status and rank are acknowledged by the Muslim community due to his virtues and excellence, and everyone is indebted to his favors, then his funeral prayer in absentia (salat al-janazah al-gha'ib) should be performed.
Hafiz Ibn Taymiyyah rahimahullah and Hafiz Ibn Qayyim rahimahullah have adopted this moderate position.
There is a difference of opinion among the four Imams (a’immah arba‘ah) on this matter.
According to Imam Shafi‘i rahimahullah and Imam Ahmad rahimahullah, the funeral prayer in absentia is permissible, because according to Imam Shafi‘i rahimahullah, the funeral prayer is a supplication (du‘a), and supplication can be made for both the present and the absent.
Hafiz Ibn Qayyim rahimahullah states:
During the lifetime of the Prophet sallallahu alayhi wa sallam, many of his companions passed away in absentia,
but the Prophet sallallahu alayhi wa sallam did not perform the funeral prayer in absentia for anyone.
The summary is that performing the funeral prayer in absentia as an acknowledgment of the services of a great personality is correct, but it is not correct for every pious person.

➌
The four Imams (a’immah arba‘ah) are in agreement that there are four takbirs in the funeral prayer.

Explanation:
1:
Najashi was the title of the king of Abyssinia, just as the title of the king of Rome was Caesar and the title of the king of Persia was Kisra. Najashi’s personal name was Ashamah ibn Abjar. It was during the reign of this king that the Muslims migrated from Mecca to Abyssinia. At the end of 6 AH or in Muharram of 7 AH, the Prophet sallallahu alayhi wa sallam invited Najashi to accept Islam through Amr ibn Umayyah al-Damri. Najashi kissed the blessed letter, placed it upon his eyes, descended from his royal throne, and accepted Islam at the hand of Ja’far ibn Abi Talib radi Allahu anhu. He wrote all these details to the Prophet sallallahu alayhi wa sallam. After the Battle of Tabuk, in the month of Rajab, 9 AH, he passed away.

2:
Some people have deduced from this the permissibility of the absentee funeral prayer (salat al-janazah ghā’iban). Regarding the absentee funeral prayer, the appropriate position is that if the funeral prayer has not been performed for the deceased, then it should be performed; and if it has already been performed, then the communal obligation (fard kifayah) has been fulfilled on behalf of the Muslims—except in the case of a respected and righteous personality, in which case it is better to perform it. This is the view of Imam Ahmad ibn Hanbal, Shaykh al-Islam Ibn Taymiyyah, and Ibn Qayyim rahimahullah. The absentee funeral prayer for ordinary Muslims is not established from the Prophet sallallahu alayhi wa sallam, nor is it the practice of the Ummah.

1948. Commentary: The intention of the Imam is that performing the funeral prayer (janazah) is a communal obligation (fard kifayah), meaning that every (Muslim) deceased must have a funeral prayer performed for them—whether a few people perform it or many—otherwise, all will be sinful. From this hadith, by implication, the permissibility of the absentee funeral prayer (janazah ghā’ib) is also established. Imam Shafi’i and Imam Ahmad rahimahullah are of this opinion, whereas the Hanafi and Maliki scholars do not hold this view. The correct position is that performing the absentee funeral prayer is permissible, and the aforementioned hadith is its evidence.

1977. Commentary: "Just as it is done for the deceased"—that is, forming rows in the funeral prayer is a well-known and undisputed matter. Moreover, the use of the word "prayer" (salah) for the funeral indicates that, apart from the specific rulings of the funeral prayer, all the general rulings of prayer apply to it as well, such as: facing the qiblah, performing ablution (wudu), straightening the rows, reciting al-Fatihah, and so on.