If I were standing in front of the Messenger of Allah ﷺ, I would have seen his armpits. Abu Majliz said, it seems he said this because he was in prayer.
أخبرنا محمد بن عبد الله بن بزيع قال حدثنا معتمر بن سليمان عن عمران عن أبي مجلز عن بشير بن نهيك
لو كنت بين يدي رسول الله ﷺ لأبصرت إبطيه قال أبو مجلز كأنه قال ذلك لأنه في صلاة
No references are available.
[Its chain of transmission is hasan] Abu Dawud narrated it, in the chapter on Prayer, in the section on whoever mentioned that he raises his hands when he stands up from the two prostrations, hadith no. 746, from the hadith of Imran, transmitted through him, and it is also found in al-Kubra, hadith no. 694.