1. During his return from the visit, the Messenger (saw) cried. The companions said, “What makes you cry, Oh Messenger of Allah?” He said, “I miss my brothers.” They said : “Are we not your brothers, Oh Messenger of Allah?” He said, “No, you are my Companions. My brothers are those who will come after me and they believe in me without seeing me.”
(Ad-Darami, At-Tabaraani, Al-Hakim)
2. Allah has given one Dua to every single prophet and every single messenger, that he has guaranteed that He will respond to. And every single prophet has used up this Dua for himself in this world, except for me. I have saved it and I have not used it and I will not use it in this life. I have kept it for my Ummah and I will use it for them on the day of judgement. And my Dua will be, O Allah, forgive my entire Ummah.
(Sahih Muslim 199)
3. A’ishah narrates “Once, when I saw the Prophet in a good mood, I said to him: “O Messenger of Allah! Supplicate to Allah for me!” So, he said: “O Allah! Forgive ‘A’ishah her past sins and her future sins, the sins which she has hidden and the sins which have been made apparent.”
So I began smiling, to the point that my head fell into the lap of the Messenger of Allah out of joy.
Messenger of Allah said to me: “Does my supplication make you happy?” I replied: “And how can your supplication not make me happy?”
He then said: “By Allah, it is the supplication that I make for my Ummah in every prayer.”
[Narrated in Al Bazzaar, Hasan Al-Albani]