Ibn Majah

Commentary:
(1)
When the soul of a believer ascends to the heavens, all the angels it passes by become happy. Upon the death of Sa'd bin Mu'adh (radi Allahu anhu), when his blessed soul ascended to the heavens, even the Divine Throne (Arsh) rejoiced at its arrival, and as an expression of this joy, movement occurred in it.

(2)
The creation of Allah, which appears lifeless and devoid of understanding in the eyes of humans, is in reality not so; rather, even inanimate creation possesses consciousness and feeling, but this is beyond human perception.

(3)
Some scholars have interpreted the joy of the Throne (Arsh) as referring to the joy of the close angels.
And Allah knows best.

Hadith Commentary:
The narration alludes to the enmity and hostility that existed between the two tribes of the Ansar, Aws and Khazraj, during the pre-Islamic era (Jahiliyyah). However, after the advent of Islam, no trace of this enmity remained. Sa’d radi Allahu anhu was the chief of the Aws tribe, and al-Bara’ radi Allahu anhu belonged to the Khazraj. The intent of Jabir radi Allahu anhu is that, due to this old rivalry, the narration was not conveyed in full detail. In any case, there are hadiths regarding both the Throne of the Most Merciful (Arsh ar-Rahman) and the “bed” (sarir) shaking, and the scholars of hadith (muhaddithun) have explained both scenarios by stating that the death of Sa’d ibn Mu’adh radi Allahu anhu was a momentous event. There is no question of diminishing his rank before anyone.

Hadith Commentary:
➊
Barā’ bin ‘Āzib (radi Allahu anhu) was astonished at how the Throne (‘Arsh) of Allah could move at the death of a servant, so he interpreted it as referring to his (Sa‘d’s) bier. He did not say this out of any enmity, but rather expressed it according to his own understanding. However, Jābir (radi Allahu anhu) thought that perhaps Barā’ bin ‘Āzib (radi Allahu anhu) was saying this for some other reason, so he clarified that whether one understands it or not, the reality is that at the death of Sa‘d bin Mu‘ādh (radi Allahu anhu), the Divine Throne (‘Arsh) itself moved. There is no room for interpretation regarding this, because I myself heard these words from the Messenger of Allah (sallallahu alayhi wa sallam).

➋
The movement of the Divine Throne (‘Arsh) was due to joy, and it is possible for the Throne of Allah to move out of happiness, just as once Mount Uhud also moved out of joy. Allah, exalted is He, is capable of all things; even some stones fall from mountains out of fear of Allah.
And Allah knows best.

Hadith Commentary: Benefits and Issues: Allah, the Exalted, has placed some degree of consciousness and perception even within inanimate objects. That is why stones also fall out of fear and awe of Allah, and if the Noble Qur’an had been sent down upon a mountain, it too would have been shattered into pieces due to humility and submissiveness. In this manner, when the soul of Sa’d ibn Mu’adh (radi Allahu anhu) departed, the Throne of Allah (Arsh al-Ilahi) swayed with joy to express happiness and delight at his arrival.

Explanation:
1:
That is: in joy at his arrival in the heavens,
some people have interpreted "the angels who bear the Throne of the Most Merciful" to mean that they swayed with happiness at Sa'd ibn Mu'adh radi Allahu anhu's arrival in the heavens.
In any case, this is evidence of his nearness and acceptance in the court of Allah.