Once the messenger of Allah was asked: with what tongue did the Lord of the universe speak with you on Al-Miraj (The night journey and the ascension of prophet Muhammad)? The Holy Prophet said: God spoke with me by the tongue of Ali Ibn Abi Talib. I asked the Lord: did you speak with me or Ali did? God said: O Ahmad! I am not like the things and neither can I be compared with people nor can I be described by things. I created you with my light and created Ali with your light. I know about everything in your heart and I found no one more beloved than Ali Ibn Abi Talib in your heart. So I speak by his tongue with you so that your heart becomes calm.
source : erfan.ir