Whenever there was drought, ʿUmar bin Al-Khattab used to ask Allah for rain through Al-ʿAbbas bin ʿAbdul Muttalib, saying, "O Allah! We used to request our Prophet to ask You for rain, and You would give us. Now we request the uncle of our Prophet to ask You for rain, so give us rain." And they would be given rain."  

اللَّهُمَّ إِنَّا كُنَّا نَتَوَسَّلُ إِلَيْكَ بِنَبِيِّنَا ﷺ فَتَسْقِينَا وَإِنَّا نَتَوَسَّلُ إِلَيْكَ بِعَمِّ نَبِيِّنَا فَاسْقِنَا قَالَ فَيُسْقَوْنَ