Chapter on the Detailed Explanation of Prayer, Including the Obligatory and Recommended, and What is Permissible and Not Permissible.

Muhammad ibn Ya’qub, from Ali ibn Muhammad, from Sahl ibn Ziyad, from Muhammad ibn Sinan, from Ibn Muskan, from Abu Basir, who said: I asked Him عليه السلام about a man who forgets the Dhuhr prayer until the time of ‘Asr enters. Imam عليه السلام said: "He begins with Dhuhr, and likewise with the (other) prayers, begin with the one you forgot, unless you fear that the time of the current prayer will end. In that case, begin with the one whose time you are in, and then make up the one you forgot."