Mishkat al-Masabih
Anas said that God’s messenger used to raise his hands in supplication so that the whiteness under his armpits was visible.
وَعَنْ أَنَسٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَرْفَعُ يَدَيْهِ فِي الدُّعَاءِ حَتَّى يُرى بياضُ إبطَيْهِ
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