Sunan Abu Dawud
1281
Sahih+3

Narrated 'Abd Allah al-Muzani: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

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid