(1) باب صَلاَةِ الْمُسَافِرِينَ وَقَصْرِهَا
Anas b. Malik is reported to have said:
I observed four rak'ahs in the noon prayer with the Messenger of Allah (ﷺ) at Medina, and said two rak'ahs in the afternoon prayer at Dhu'l-Hulaifa.
Reference: Sahih Muslim 690 b
In-book reference: Book 6, Hadith 13
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1470