It was narrated that Sa"ed bin al-Musayyab said: I said to Sa’d bin Malik:

I want to ask you about a hadeeth, but I feel too shy to ask you about it. He said: Do not feel like that, O son of my brother. If you know that I have some knowledge then ask me about it and do not feel too shy of me. I said: What did the Messenger of Allah (ﷺ) say to ‘Ali when he left him in charge of Madinah during the campaign to Tabook? Sa"d said: The Prophet (ﷺ) left Ali in charge of Madinah during the campaign to Tabook, and he [‘Ali] said: O Messenger of Allah, are you leaving me behind with those who are staying behind, the women and children? He said: “Does it not please you to be to me as Haroon was to Moosa?” He said: Yes, O Messenger of Allah. Then he turned and rushed back, and it is as if I can see the dust kicked up by his feet. And Hammad said: And ‘Ali went back quickly.