Hadith 1507
Chapter 3: The recommended condition for the imam to be in if he goes out - كتاب الاستسقاء
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبْدُ الْعَزِيزِ، عَنْ عُمَارَةَ بْنِ غَزِيَّةَ، عَنْ عَبَّادِ بْنِ تَمِيمٍ، عَنْ عَبْدِ اللَّهِ بْنِ زَيْدٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم اسْتَسْقَى وَعَلَيْهِ خَمِيصَةٌ سَوْدَاءُ .
It was narrated from Abdullah bin Zaid that:
The Messenger of Allah (ﷺ) prayed for rain wearing a black khamisah.
Reference : Sunan an-Nasa'i 1507
In-book reference : Book 17, Hadith 4