It is narrated from Hazrat Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) used to raise his hands so high that the whiteness of his blessed armpits would become visible.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 13187
Hadith Gradingحکم دارالسلام:إسناده صحيح من حدیث ثابت، خ: 1031، م: 896 وعلی بن زید بن جدعان ضعیف