(35) باب الصَّلاَةِ قَبْلَ الْمَغْرِبِ
Narrated `Abdullah Al-Muzni:
The Prophet (ﷺ) said, "Pray before the Maghrib (compulsory) prayer." He (said it thrice) and in the third time, he said, "Whoever wants to offer it can do so." He said so because he did not like the people to take it as a tradition.
Reference: Sahih al-Bukhari 1183
In-book reference: Book 19, Hadith 60
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 21, Hadith 277