question #3 Sahih al-Bukhari 1000, Book 14, Hadith 11 : What is the distinction between obligatory and voluntary prayers in terms of their performance during travel?

The Prophet (ﷺ) used to offer (Nawafil) prayers on his Rahila (mount) facing its direction by signals, but
not the compulsory prayer. He also used to pray witr on his (mount) Rahila.