question #1 Sahih al-Bukhari 143, Book 4, Hadith 9 : What is the significance of making supplications for others in Islam?

Once the Prophet (ﷺ) entered a lavatory and I placed water for his ablution. He asked, “Who placed it?”
He was informed accordingly and so he said, “O Allah! Make him (Ibn `Abbas) a learned scholar in
religion (Islam).