Musnad Ishaq

Benefits:
It is established from other authentic ahadith that during the prayer for rain (istisqa’), he would raise his hands higher. (Bukhari: 3565; Muslim: 996)
Istisqa’ means to seek water; when there is a need for rain and it does not come, on such occasions the Messenger of Allah (sallallahu alayhi wa sallam) would supplicate and perform two units of prayer in congregation. In another hadith, it is mentioned that the Messenger of Allah (sallallahu alayhi wa sallam) would not raise his hands in any supplication except during the prayer for rain, when he would raise them so high that the whiteness of his armpits would become visible. (Bukhari, no. 1031; Sunan Ibn Majah, no. 1180)

This does not mean at all that he did not raise his hands for other supplications; rather, it means that in the prayer for rain, he would raise his hands higher, while in other supplications he would raise them less high. As Imam Nawawi rahimahullah has stated, what is meant is an exaggerated raising of the hands, i.e., except for istisqa’, he would not raise his hands so much in other situations. (Sharh Muslim by Nawawi: 1/293)