Riyad as-Salihin, Book 9, Hadith 1122 (In-Book) ⓘ
'Abdullah bin Mughaffal (May Allah be pleased with him) reported: The Prophet said, "Perform two Rak'ah before Maghrib prayer." He repeated it twice; when repeating it for the third time he added: "He who may so wish."[Al- Bukhari].
وعن عبد الله بن مغفل، رضي الله عنه عن النبي صلى الله عليه وسلم قال: "صلوا قبل المغرب" قال في الثالثة: "لمن شاء" ((رواه البخاري)).