Sunan Abi Dawud Book 5, Hadith 32
The Messenger of Allah (ﷺ) said: Pray two rak'ahs before the Maghrib prayer. He then said (again): Pray two rak'ahs before the Maghrib prayer, it applies to those who wish to do so. That was because he feared that the people might treat it as sunnah.
Dhakwan, the client of Aisha, reported on the authority of Aisha: The Messenger of Allah (ﷺ) used to pray after the afternoon prayer but prohibited others from it; and he would fast continuously but forbid others to do so.
I offered two rak'ahs of prayer before the Maghrib prayer (i.e. obligatory) during the time of the Messenger of Allah (ﷺ). I (narrator al-Mukhtar b. Fulful) asked Anas: Did the Messenger of Allah (ﷺ) se you ? He replied: Yes, but he neither commanded us nor forbade us (to do so).