A bedouin came to Messenger of Allah ﷺ on a Friday and said, "O Messenger of Allah ! The livestock, the offspring, and the people have perished." So, Messenger of Allah ﷺ raised both his hands invoking Allah (for rain) and the people too raised their hands with Messenger of Allah ﷺ invoking Allah (for rain). We had not left the mosque when it started raining. It rained till the next Friday when the same man came to Messenger of Allah ﷺ and said, "O Messenger of Allah! The travelers are compelled to postpone their journeys (because of excessive rain) and the roads are overflowed."  

أَتَى رَجُلٌ أَعْرَابِيٌّ مِنْ أَهْلِ الْبَدْوِ إِلَى رَسُولِ اللَّهِ ﷺ يَوْمَ الْجُمُعَةِ فَقَالَ يَا رَسُولَ اللَّهِ هَلَكَتِ الْمَاشِيَةُ هَلَكَ الْعِيَالُ هَلَكَ النَّاسُ فَرَفَعَ رَسُولُ اللَّهِ ﷺ يَدَيْهِ يَدْعُو وَرَفَعَ النَّاسُ أَيْدِيَهُمْ مَعَهُ يَدْعُونَ قَالَ فَمَا خَرَجْنَا مِنَ الْمَسْجِدِ حَتَّى مُطِرْنَا فَمَا زِلْنَا نُمْطَرُ حَتَّى كَانَتِ الْجُمُعَةُ الأُخْرَى فَأَتَى الرَّجُلُ إِلَى نَبِيِّ اللَّهِ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ بَشِقَ الْمُسَافِرُ وَمُنِعَ الطَّرِيقُ  

The narrator Anas added that the Prophet ﷺ raised his hands (during the invocation) to such an extent that the whiteness of his armpits was visible.  

عَنِ النَّبِيِّ ﷺ أَنَّهُ رَفَعَ يَدَيْهِ حَتَّى رَأَيْتُ بَيَاضَ إِبْطَيْهِ