Muhammad ibn Ali ibn Mahbub from Yaqub ibn Yazid from Ibn Abi Umayr from Abu Ayyub from Abu Abdillah عليه السلام, peace be upon him, who said: I asked Imam al-Sadiq عليه السلام about shortening (the prayer). Imam عليه السلام said: “At two ‘barid’ (‘buridayn’) or the brightness of a day (‘bayad yawm’).”