As for what was narrated by Ali ibn Ibrahim from his father from Ibn Abi 'Umayr from Jamil from Zurarah from Abu Ja’far عليه السلام, peace be upon him, who said: Imam al-Baqir عليه السلام said: “Shortening (the prayer, ‘al-taqsir’) is at a ‘barid’, and a ‘barid’ is four ‘farsakh’.”