مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 2253
Supplications
Section 3
وَعَنْ أَنَسٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَرْفَعُ يَدَيْهِ فِي الدُّعَاءِ حَتَّى يُرى بياضُ إبطَيْهِ
Anas said that God’s messenger used to raise his hands in supplication so that the whiteness under his armpits was visible.
Mishkat al-Masabih, 2253لم تتمّ دراسته (الألباني)