Sahih Muslim 898
Anas (b. Malik) reported: It rained upon us as we were with the Messenger of Allah ﷺ. The Messenger of Allah ﷺ removed his cloth (from a part of his body) till the rain fell on it. We said: Messenger of Allah, why did you do this? He said: It is because it (the rainfall) has just come from the Exalted Lord.
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا جَعْفَرُ بْنُ سُلَيْمَانَ، عَنْ ثَابِتٍ الْبُنَانِيِّ، عَنْ أَنَسٍ، قَالَ قَالَ أَنَسٌ أَصَابَنَا وَنَحْنُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم مَطَرٌ قَالَ فَحَسَرَ رَسُولُ
• Sahih Muslim 898
• Sahih Muslim Vol. 2, Book of Prayers, Hadith 1960
• Sahih Muslim, Book of Prayers, Hadith 1960