Bukhari

Hadith Commentary:
Both of these ahadith establish that even now, if the opportunity arises, these two rak‘ahs can be performed before Maghrib.
Although performing them is not obligatory, if someone does perform them, it will certainly be a cause of reward and merit.
Some people have said that later on, performing them was prohibited.
This is completely incorrect; in the previous pages, the recommendation (istihbab) of these two rak‘ahs has already been elucidated.
‘Abdullah ibn Malik al-Juthami was a Tabi‘i Mukhadram, meaning he was present during the time of the Prophet (sallallahu alayhi wa sallam), but did not meet him. He came to Egypt during the era of ‘Umar (radi Allahu anhu), and then remained there.
A group has counted him among the Companions (Sahabah).
From this hadith, it is also derived that the time for Maghrib is lengthy, and the statement of one who considers it short is without evidence.
However, it is recommended (mustahabb) to perform these rak‘ahs before the congregation (jama‘ah) stands for prayer.
(Wahidi)

Hadith Commentary:
(1)
Qadi Abu Bakr ibn al-‘Arabi says that after the noble Companions (radi Allahu anhum), no one performed these two rak‘ahs.
This hadith refutes that statement because Abu Tamim was a Tabi‘i (Successor) and he performed them.
(Fath al-Bari: 3/73)
It is narrated from Anas (radi Allahu anhu) that when the mu’adhdhin would call the adhan for Maghrib in Madinah Munawwarah, we would all rush towards the pillars and perform two rak‘ahs.
People would perform these two rak‘ahs in such abundance that a stranger would think that the Maghrib prayer had already been offered (and now the subsequent two rak‘ahs are being performed).
(Sahih Muslim, Salat al-Musafirin, Hadith: 1939(837))
It is also narrated from Anas (radi Allahu anhu) that we would perform two rak‘ahs after sunset and the Messenger of Allah (sallallahu alayhi wa sallam) would be watching us.
He neither commanded us to do so nor forbade us from it.
(Sahih Muslim, Salat al-Musafirin, Hadith: 1938(835))
In one narration of Sahih al-Bukhari, it is mentioned that when the Messenger of Allah (sallallahu alayhi wa sallam) would come out of his house to lead the Maghrib prayer, he would see people performing prayer.
(Sahih al-Bukhari, al-Adhan, Hadith: 625)
(2)
Those who wish to perform this Sunnah before Maghrib prayer should be prepared beforehand, i.e., be in a state of ablution (wudu), and as soon as the adhan is called, they should begin performing it so that there is no delay in the performance of the Maghrib prayer.