The story of Muaz is mentioned. He said that the Prophet ﷺ asked the young man, "What do you do, nephew, when you pray?"The young man replied, "I recite the opening of the Book, then I ask Allah for Paradise and seek refuge in Him from the Fire. I cannot match your soft murmuring, nor that of Muaz."The Messenger of Allah ﷺ said, "Muaz and I murmur around these very things," or something to that effect.
حدثنا يحيى بن حبيب حدثنا خالد بن الحارث حدثنا محمد بن عجلان عن عبيد الله بن مقسم
ذكر قصة معاذ قال وقال يعني النبي ﷺ للفتى كيف تصنع يا ابن أخي إذا صليت قال أقرأ بفاتحة الكتاب وأسأل الله الجنة وأعوذ به من النار وإني لا أدري ما دندنتك ولا دندنة معاذ فقال رسول الله ﷺ إني ومعاذا حول هاتين أو نحو هذا
[Hasan] Ahmad narrated it: 3/302, from the hadith of Muhammad bin Ajlan, with the same wording, and he explicitly stated that he heard it directly. Ibn Khuzayma graded it sahih, hadith: 1634. See also the previous hadith and hadith: 599.