The Prophet ﷺ prayed in my chamber, and the people followed his prayer from outside the chamber, praying along with him.
حدثنا هشيم قال أنبأنا يحيى بن سعيد عن عمرة
صلى النبي ﷺ في حجرتي والناس يأتمون به من وراء الحجرة يصلون بصلاته
Its isnad is sahih. Amrah is the daughter of Abdul-Rahman bin Saad the Ansari, trustworthy, and her hadith is found in the collections of all six. The hadith is in Bukhari 3/10, number 1129, in the chapter on tahajjud, on the Prophet's ﷺ encouragement to pray at night. There is no doubt that the hadith refers to the voluntary prayer.