Ahmad ibn Muhammad ibn Isa, from Hammad ibn Uthman, from Hariz, from Zurarah, from Abu Ja’far عليه السلام, peace be upon him, who said: I said to Imam al-Baqir عليه السلام: “What do you say about someone who arrives in a town, until when should he remain shortening (his prayer), and when should he complete it (his prayer in full)?” Imam عليه السلام said: “If you enter a land and you are certain (‘ayqanta’) that you will stay there for ten days, then complete the prayer (‘atimm al-salat’). But if you do not know how long your stay will be there, saying, ‘Tomorrow I will leave,’ or ‘the day after tomorrow,’ then shorten (your prayer) until a month passes. When a full month has passed for you, then complete the prayer even if you intend to leave at that very moment.”