(1) باب صَلاَةِ الْمُسَافِرِينَ وَقَصْرِهَا
Ibn 'Abbas reported:
Allah has prescribed the prayer through the word of your Prophet (ﷺ) as four rak'ahs when resident, two when travelling, and one when danger is present. (JA)
Reference (JA): Sahih Muslim 687 a (JA)
In-book reference (JA): Book 6, Hadith 6 (JA)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1463 (JA)