The obligatory prayer of travel is two units, except for Maghrib, for surely, the Messenger of Allah (s) left it upon its state in travel and residence. One does not pray anything of the voluntary prayers of the day in travel, and one does not leave off anything of the voluntary prayers of the night. Night Prayer (salat al-layl) is not permissible from the beginning of the night except for in travel. When the person does its expiation (qada) then it is better for him than praying it in the beginning of the night.