It is narrated from the Prophet of Islam (PBUH) who said:

Allah (SWT) has allocated an accepted Dua for every prophet, and the past prophets have used that Dua in this world; but I have kept that Dua to intercede (Shafa’at) for my Ummah in the hereafter. And my intercession will be for those individuals in my Ummah who pass away from this world as believers and they are not Moshrik (polytheist) [1].

[1] Sonan Ibn Majah, Vol. 2, Page 1443, narrated from Manshoor Javid, Vol. , Page 155.

Source; en.shafaqna.com