It is narrated from Sayyiduna Khawwat bin Jubayr (may Allah be pleased with him); he said: I was praying when a man behind me said: "Make it light, for we need you for something." I turned around and it was the Messenger of Allah (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4135