Rain fell upon us while we were with the Messenger of Allah ﷺ. The Messenger of Allah ﷺ went out and uncovered part of his garment so that the rain touched him.We asked, "Messenger of Allah, why did you do this?"He replied, "Because it has just come from its Lord."
حدثنا عفان حدثنا جعفر بن سليمان حدثنا ثابت
أصابنا مطر ونحن مع رسول الله ﷺ فخرج رسول الله ﷺ فحسر ثوبه حتى أصابه فقلنا يا رسول الله لم صنعت هذا قال إنه حديث عهد بربه
Its isnad is sahih. Jafar bin Sulayman Dubai was deemed trustworthy despite leanings toward Shia views found in him, and he has narrations in Muslim's collection.The hadith was narrated by Muslim, 2/615, number 898, in the book of seeking rain, the chapter on supplication when seeking rain, and by Ibn Abu Shayba, 8/555, in the book of manners, the chapter on those who exposed themselves to rain for the first time.