Is attendance to the Prophet more important than salah/prayer?

In the event when the was sun returned, technically rose from west to east, after having set. > [.. the revelation from Allah descended upon His Prophet, peace be upon him and his progeny, and it overwhelmed him. Ali b. Abi Talib, may peace be upon him, covered him (i.e. the Prophet) with his cloth, till the sun set. When the revelation ceased, the Prophet, peace be upon him and his progeny, said: "O Ali! Have you offered your Asr prayers?" He said: "No O, messenger of Allah! My attendance upon you prevented me from that." Then the Prophet, peace be upon him and his progeny, prayed: "O Allah, cause the sun to return for Ali b. Abi Talib". The sun had set, so it rose again till its rays reached my room and half the height of the Mosque."](http://imamreza.net/eng/imamreza.php?id=3661) Why was Ali (as)'s attendance to Muhammad (saww) more important than salah/prayer?* Was that a special case?* Or is it a general rule that attendance of the Prophet(saww), when in need, takes precedence over salah/prayer and/or other obligations? Bonus question: Which surah(s)/chapter(s) and ayah(s)/verse(s) was/were being revealed? *Note: The authenticity of the above mentioned event is not under question here.* *those who consider this event inauthentic may skip it because this is not the main purpose of this question