Sahih Ibn Khuzaymah 1635 — 131| Chapter clarifying that Mu‘adh prayed

It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that Sayyiduna Mu'adh (may Allah be pleased with him) used to perform the 'Isha prayer with the Messenger of Allah (peace be upon him), then return and lead his companions in prayer. Imam Abu Bakr (may Allah have mercy on him) says that I have already written this issue in detail. I have mentioned in this issue the ahadith of the Noble Prophet (peace be upon him) regarding the prayer of fear, that the Noble Prophet (peace be upon him) led one group in a voluntary prayer while they performed the obligatory prayer behind him. Thus, that prayer was voluntary for the Noble Prophet (peace be upon him) and obligatory for them.