Al-Husayn ibn Sa’id, from Safwan, from al-Ala’, from Muhammad ibn Muslim, who said: I said to Abu Abdillah عليه السلام, peace be upon him: “A man intends to travel and he departs, when should he begin shortening (his prayer)?” Imam عليه السلام said: “When he disappears from the houses (‘tawara min al-buyut’).” I asked: “A man intends to travel and he departs when the sun has passed its zenith (zawal al-shams).” Imam عليه السلام said: “When you set out, then pray two rak‘ahs.”