When the Messenger of Allah ﷺ prostrated, he would hold his arms away from his sides until the whiteness of his armpits could be seen.
كان رسول الله ﷺ إذا سجد جافى حتى يرى بياض إبطيه.
Imam Ahmad narrated it (14138), saying, Abdul-Razzaq narrated to us (it is also found in his Musannaf, 2922), Maamar narrated to us, from Mansur, from Salim bin Abu Jaad, from Jabir, and he related the hadith. Its chain is sahih. Maamar is Ibn Rashid, and Mansur is Ibn Mutamir. As for Salim bin Abu Jaad, although he is trustworthy, he frequently transmits with a broken chain from senior companions, but his hearing directly from Jabir bin Abdullah and Anas bin Malik has been established, as noted in Jami Tahsil (218).Ibn Khuzayma also graded the hadith sahih, recording it (649) by way of Abdul-Razzaq, with the same wording. Haythami said in Majma al-Zawaid (1/125), Ahmad and Tabarani in his three books narrated it, and the men of Ahmad's chain are the men of the sahih.