This hadith has been narrated by Ja'far bin Rabi' with the same chain of transmitters. And in the narration transmitted by 'Amr bin al-Harith (the words are): "When the Messenger of Allah (ﷺ) prostrated, he spread out his arms so that the whiteness of his armpits was visible." And in the narration transmitted by al-Laith (the words are: "When the Messenger of Allah (ﷺ) prostrated, he spread his hands from the armpits so that I saw their whiteness."