It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he said: "It is as though I can see the whiteness of the armpits of the Messenger of Allah (peace and blessings be upon him) when he (peace and blessings be upon him) prostrated."
No one narrated this hadith from Salih, the freed slave of al-Taw'amah (may Allah have mercy on him), except Sa'id bin Abi Ayyub (may Allah have mercy on him), and Rawh bin Salah (may Allah have mercy on him) is alone in narrating it.
Hadith Referenceالمعجم الأوسط / باب الألف / 221
Hadith Takhrij«أخرجه الحاكم فى «المستدرك» برقم: 836، وأحمد فى «مسنده» برقم: 11282، 11283، والبزار فى «مسنده» برقم: 9382، وابن حجر فى «المطالب العالية» برقم: 506، والطحاوي فى «شرح معاني الآثار» برقم: 1384، 1388»