Anas (May Allah be pleased with him) reported:
In the lifetime of the Messenger of Allah (ﷺ), we used to perform two Rak'ah (optional prayer) after sunset before the Maghrib prayer. It was asked: "Did Messenger of Allah (ﷺ) perform them?" He replied: "He saw us performing it, but he neither ordered us to perform them nor did he forbid us from doing so."[Muslim].
App reference: Book 9, Hadith 134
Arabic/English book reference: Book 9, Hadith 1124