Riyad us Saliheen: Hadith 714

I sought permission of the Prophet (ﷺ) to perform 'Umrah, and he granted me leave and said, "Brother, do not forget us in your supplications." I would not exchange these words of his for the whole world.

Another narration is: He (ﷺ) said, "Include us, my brother, in your supplications."

[Abu Dawud and At- Tirmidhi].