It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that once I saw the Prophet (peace and blessings of Allah be upon him) in the state of prostration, and I saw the whiteness of the blessed armpits of the Prophet (peace and blessings of Allah be upon him).
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 2753
Hadith Gradingحکم دارالسلام:صحيح لغيره، شريك سيئ الحفظ لكنه توبع ، وأربد لم يرو عنه غير أبى إسحاق