(1) باب صَلاَةِ الْمُسَافِرِينَ وَقَصْرِهَا
Ibn 'Abbas reported:
Allah has prescribed the prayer by the tongue of your Apostle (ﷺ) as two rak'ahs for the traveller, four for the resident, and one in danger. (ID)
Reference (ID): Sahih Muslim 687 b (ID)
In-book reference (ID): Book 6, Hadith 7 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1464 (ID)