Ahmad ibn Muhammad ibn Isa narrated from Ali ibn Al-Hakam from Abu Ayyub from Isma'il ibn Jabir who said: I said to Abu Abdillah عليه السلام, peace be upon him: “I get occupied (and cannot pray at the usual time)”. Imam عليه السلام said: "Then do as we do, pray six rak'ahs when the sun is at the same position it is at during the Asr prayer,” (meaning at the height of the greater forenoon ‘al-duha al-akbar’), “and count them as if you had performed them at zawal (midday)."