مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1499
Prayer
Prayer for Rain - Section 1
وَعَنْ أَنَسٍ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اسْتَسْقَى فَأَشَارَ بِظَهْرِ كَفَّيْهِ إِلَى السَّمَاءِ. رَوَاهُ مُسلم
He said the Prophet (ﷺ) prayed for rain pointing the back of his hands to the sky. Muslim transmitted it.
Mishkat al-Masabih, 1499صَحِيح (الألباني)