Sahih al-Bukhari 15:5
Narrated Anas:
Whenever drought threatened them, `Umar bin Al-Khattab, used to ask Al-Abbas bin `Abdul Muttalib to invoke Allah for rain. He used to say, "O Allah! We used to ask our Prophet to invoke You for rain, and You would bless us with rain, and now we ask his uncle to invoke You for rain. O Allah ! Bless us with rain."(1) And so it would rain.
Reference
Sahih al-Bukhari 15:5
In-book reference
Book 15, Hadith 5
Arabic Text
حَدَّثَنَا الْحَسَنُ بْنُ مُحَمَّدٍ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الأَنْصَارِيُّ، قَالَ حَدَّثَنِي أَبِي عَبْدُ اللَّهِ بْنُ الْمُثَنَّى، عَنْ ثُمَامَةَ بْنِ عَبْدِ اللَّهِ بْنِ أَنَسٍ، عَنْ أَنَسٍ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ كَانَ إِذَا قَحَطُوا اسْتَسْقَى بِالْعَبَّاسِ بْنِ عَبْدِ الْمُطَّلِبِ فَقَالَ اللَّهُمَّ إِنَّا كُنَّا نَتَوَسَّلُ إِلَيْكَ بِنَبِيِّنَا فَتَسْقِينَا وَإِنَّا نَتَوَسَّلُ إِلَيْكَ بِعَمِّ نَبِيِّنَا فَاسْقِنَا. قَالَ فَيُسْقَوْنَ.