‘Ali bin abi Haraarah (rahimahullah) narrates:

My mother had been crippled for twenty years. One day, she said to me, “Go to Imaam Ahmed bin Hambal (rahimahullah) and ask him to make du‘aa to Allah Ta‘ala for me (to be cured).”

I thus went to the home of Imaam Ahmed (rahimahullah) and knocked on the door. Imaam Ahmed (rahimahullah) was in the house, close to the door, and did not open the door. Rather, he called out, “Who is it?” I replied, “I am a person who lives in such-and-such area. My mother, who is crippled, asked me to request you to make du‘aa for her (to be cured).”