(27) بَابُ نَهْيِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَلَى التَّحْرِيمِ إِلاَّ مَا تُعْرَفُ إِبَاحَتُهُ
Narrated `Abdullah Al Muzam:
The Prophet (ﷺ) said, "Perform (an optional) prayer before Maghrib prayer." (He repeated it thrice) and the third time he said, "Whoever wants to offer it can do so," lest the people should take it as a Sunna (tradition). (See Hadith No. 277, Vol. 2)
Reference: Sahih al-Bukhari 7368
In-book reference: Book 96, Hadith 95
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 92, Hadith 465